Emissions Report Methodology

Current Section: data resources

Weekly Emissions Report Methodology (US)

Data for the Genscape Weekly Emissions Report is derived using historical emissions patterns reported by the US Environmental Protection Agency in its quarterly release of Continuous Emissions Monitoring data. The Genscape calculation takes behavior at different load levels and during different seasons and matches it with the observed hourly output at plants monitored by Genscape to arrive at an hourly emissions estimate.

Plants monitored by Genscape account for 47pc of all US SO2 emissions and 45pc of all NOx emissions in the SIP Call states. Over a period of 27 months (Jan 2002 to Mar 2004), the plants monitored by Genscape showed a correlation with total emissions of 0.97 for nationwide SO2 and 0.94 for SIP Call NOx.

The Genscape Emissions Index is calculated using the coverage figures described above to arrive at a total estimated amount of emissions.

The percentage figures in the allocation comparison tables show year-to-date and season-to-date cumulative amounts compared to initial allocations. The percentage figures do not take purchases or sales of allowances into account. For the cumulative figures, EPA data is used where possible, supplemented by Genscape estimates where EPA data is not yet available.

Plants that have added selective catalytic reduction equipment since the 2003 season, and for which there is no historical data of emissions using that equipment have their calculated output adjusted using a factor derived from historical reductions at plants during the first season of SCR operation.

For 2004, the NOx season is calculated differently for the states that joined the NOx SIP Call that year. The incumbent Northeastern states’ season cumulative figures are calculated from May 1, while the new entrants’ cumulatives are calculated from May 31.