Nevada Greenhouse Gas Inventory and Reference Case Projections

FINAL Nevada GHG Inventory and Reference Case Projection
CCS, July 2007
production-based emissions while the subsequent section, Electricity trade and the allocation of
GHG emissions, reports consumption-based emissions.
As displayed in Figure A3, coal and natural gas were used to generate the vast majority (over
90%) of Nevada’s electricity in 2004. Since coal generation yields higher GHG emissions per
MWh generated than natural gas, coal accounts for 70 percent of the GHG emissions from power
plants in Nevada. Table A2 reports the emissions from the five plants in Nevada with the highest
emissions from 2000 to 2005. The plant with the highest GHG emissions, Mohave, accounted for
about 40 percent of Nevada’s GHG emissions. Mohave went into temporary shut down at the
end of 2005, leading to a large decrease in GHG emissions in 2006, as will be discussed in the
results section. The Nevada Power Company owned 14% of the Mohave generating station with
Southern California Edison, City of Los Angeles and the Salt River Project of Arizona owning
the remainder. 14 Electricity trade and GHG allocation are discussed in section below.
We considered two sources of data in developing the historic inventory of GHG emissions from
Nevada power plants – EIA State Energy Data (SED), which need to be multiplied by GHG
emission factors for each type of fuel consumed, and EPA data on CO 2 emissions by power
plant. For total electric sector GHG emissions, we used the EIA’s SED rather than EPA data
because of the comprehensiveness of the EIA-based data. The EPA data are limited to plants
over 25 MW and include only CO 2 emissions (EPA does not collect data on CH 4 or N 2 O
emissions). Through discussions with EPA we also learned that EPA data tend to be conservative
(i.e., overestimate emissions) because the data are reported as part of a regulatory program, and
that during early years of the data collection program, missing data points were sometimes
assigned a large value as a placeholder. However, EPA provides easily accessible data for each
power plant (over 25 MW), which would be much more difficult to extract from EIA data, and
the CO 2 emissions from the two sources differ by less than 2 percent in most years. Based on this
information, we chose to report both data sources but rely on the EIA data for the inventory
values. For total GHG emissions from electricity production in Nevada, we applied SGIT
emission factors to EIA’s SED. For CO 2 emissions from individual plants, we used the EPA
database.
14 Information from EPA’s Emission & Generation Resource Integrated database (EGRID),
http://www.epa.gov/cleanenergy/egrid/index.htm.
Nevada Division of 17 Center for Climate Strategies
Environmental Protection
www.climatestrategies.us