Greenhouse Gas Protocol methodology for US grid electricity

Contents

Summary

This methodology represents carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and CO2e emissions associated with subregions of the United States electricity grid. The data is based upon the Greenhouse Gas Protocol spreadsheet tool for purchased electricity, version 4.2. It represents data from the year 2005.

The methodology

Emissions model

This methodology is based upon emissions factors which represent the rate at which emissions occur in relation to quantities of electricity consumed. Multiplying a quantity of electricity consumed by these emissions factors results in an estimate of the emissions associated with that quantity.

Two regional aggregation schemes are represented:

  • eGRID containing 26 subregions
  • NERC (North American Electric Reliability Corporation) containing 8 subregions

These regions are not mutually exclusive but overlap - typically one NERC region may cover several eGrid regions. See the 'gallery' for maps of the respective regions.

Model data

The emissions intensity of grid electricity varies according to specfic grid sub-regions. Each grid sub-region is represented by it's own characteristic emissions intensity related to the specific mix of generating technologies employed wihtin each region. 26 eGRID and 8 NERC regions are represented which are, in-turn, represented by a characteristic CO2, CH4 and N2O emissions intensities.

Activity data required

The quantity of electricity generated is required to make a calculation.

The Greenhouse Gas Protocol worksheets additionally provide functionality for the accounting of electricity usage in shared facilities. This calculation is based on the proportion of floor area which is under consideration (e.g. square feet of office space). In this case the 'responsible' and 'total' areas should also be provided.

Calculation and result

By default, the quantities returned represent the CO2, CH4, N2O and CO2e emissions associated with the subregion and the total quantity of energy specified. If values for the 'responsible' and 'total' areas are provided the returned value represents just the emissions attributable to the area under consdsideration.


Related methodologies

The direct representation of the US Environmental Protection Agency eGRID dataset is available. Emissons methodologies are based on various geographic breakdowns of the United States: eGRID region, NERC region, state and Power Control Area. These datasets are up to date with respect to the EPA publications, and include additional pollutants and transmisson losses.


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