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          Carbon Emissions Were Estimated


How the 
          Carbon Emissions Were Estimated

        Carbon 
          dioxide emissions are the main component of greenhouse gas emissions 
          caused by human activity. Carbon dioxide is emitted mostly as a byproduct 
          of the combustion of fossil fuels for energy, although certain industrial 
          processes (e.g., cement manufacture) also emit carbon dioxide. The estimates 
          of energy-related carbon emissions require both data on the energy use 
          and carbon emissions coefficients relating energy use to the amount 
          of carbon emitted.
        The Energy 
          Information Administration (EIA) is the main source of data on U.S. 
          energy use. Emissions 
          of Greenhouse Gases in the United States 1998 used annual data 
          provided by energy suppliers. However, to obtain more detail on how 
          different sectors use energy, the emissions estimates in Energy 
          and GHG Analysis rely data from on surveys of energy users, 
          such as manufacturing establishments and commercial buildings.
        All carbon 
          emissions estimates in "Energy-Related Carbon Emissions Estimates in 
          Manufacturing" were based on tables published in Manufacturing 
          Consumption of Energy 1994, the main data publication of the 1994 
          Manufacturing Energy Consumption Survey (MECS). The MECS is a national 
          sample of 22,000 manufacturing establishments, subsampled from the Census 
          of Manufactures and conducted for EIA by the Bureau of the Census. The 
          carbon emissions estimates were based on the total first use of energy, 
          which accounts for all energy sources delivered to manufacturers, regardless 
          of subsequent use. Total first use of energy includes both energy used 
          as a fuel and energy used for nonfuel (feedstock) purposes. (For 
          detailed MECS energy definitions, see Calculation 
          of MECS Energy Measures.)
        The same 
          emissions coefficients (relating carbon emissions to energy use), and 
          the same estimation procedures, were used in both Emissions of Greenhouse 
          Gases in the United States 1998 and "Energy-Related Carbon Emissions 
          Estimates in Manufacturing". The coefficients originated with the Intergovernmental 
          Panel on Climate Change (IPCC), with additional coefficients for additional 
          energy sources covered by EIA surveys. More details on the estimation 
          methodology can be found in Appendix A of the Greenhouse Gases report.
        The basic 
          emissions coefficients, giving the amount of carbon released at full 
          combustion, are contained in Table 
          B1 of that report. The emissions coefficients in Table B1 represent 
          the maximum theoretical amount of carbon that could be released from 
          the energy source. In practice, nearly all the carbon is released during 
          combustion for fuel use, but significant proportions are sequestered 
          when potential energy sources are used other than as fuel. Table 
          A2 in the Greenhouse Gases report gives the proportions 
          of the carbon assumed to be released by different uses of energy sources.
        Table 
          B1 of the Greenhouse Gases report does not contain a coefficient 
          for electricity use. The coefficient used for electricity was calculated 
          as the total amount of carbon emitted to generate electricity (calculated 
          from Table 16 of the State 
          Energy Data Report) divided by the total Btu value of net electricity 
          delivered to end-users (calculated from Tables 12 through 15 of the 
          State Energy Data Report).
        Given 
          energy data (for both fuel and nonfuel use) and emissions coefficients, 
          carbon emissions were estimated as the product of the quantity of energy 
          used (Btu value), the emissions coefficient (Table B1), and the proportion 
          emitted (Table A2).
        [Energy-Related 
            Carbon Emissions in Manufacturing]
        
        Contact:
          Stephanie 
            Battles
          Stephanie.Battles@eia.doe.gov
          (Phone: 
            (202) 586-7237)
          FAX: 
            202-586-0018**Contact Us**
        URL: http://www.eia.gov/emeu/efficiency/carbon_emissions/estn_method.html File Last Modified: May 31, 2000