Nevada Statewide Greenhouse Gas Emissions Inventory and Projections
Nevada Statewide Greenhouse Gas Emissions Inventory and Projections, 1990 to 2030
4.
4.1
Transportation
Overview
The transportation sector has been and continues to be a significant source of GHG emissions in the
state, second only to the electricity generation sector (Section 3). However, with the continued
shutdown of coal-fired electric generating units across the state and the adoption of natural gas and
renewable energy generation (e.g., solar, wind, and geothermal), the transportation sector is projected
to exceed the electricity generation sector in terms of emissions as early as 2015 and will become the
largest source of GHG emissions in the state.
Historical and projected emissions for the transportation sector were calculated based on the SIT. The
GHGs calculated in this sector are CO2, CH 4, and N2O. CO2 emissions from vehicles are considered to be
relatively easy to estimate as they are the result of fossil fuel combustion and can be directly related to
the type of fossil fuel and the amount combusted. CH 4 and N2O emissions from gasoline and diesel-
powered vehicles are the result of complex combustion dynamics that, while dependent on many
factors like installed vehicle technologies, air-to-fuel ratio, temperature, and other characteristics, can
only be estimated to a degree of certainty. Emissions from alternative fuel vehicles are also considered.
In estimating CO₂ emissions, the SIT depends on information from the EIA-SEDS to perform its
calculations. The EIA-SEDS provides fuel consumption estimates for the transportation sector at the
state level. It does this by calculating fuel consumption on a multi-state, regional level and then
distributing the results back to the individual states in the region. 21 When projecting emissions, it takes
into consideration the average fuel consumption of recent years in order to get future consumption
estimates at a multi-state, regional level before redistributing the results back to the states in the
region. In order to estimate CH and N2O emissions (minor contributors to total sector emissions), the
types and conditions of vehicles, vehicle fuel types, and vehicle miles of travel (VMT), each in a given
year, are needed. CH4 and N2O emissions are estimated by disaggregating said data into different
vehicle categories and classes of age (using national averages) and applying emissions factors for various
vehicle attributes. The SIT provides estimates for all of the needed data and provides opportunities for
states to replace the data when and if they have more refined estimates (typically generated by
state/local entities) they would prefer to use.
4.2
Historical Emissions
Historical emissions from the transportation sector peaked in 2007 at 18.508 MMTCO2eq and this
appears to have been due to the economic recession. In 2013, emissions were estimated to be 14.492
MMTCO2eq. Figure 4-1 illustrates total sector emissions compared to VMT and also compared to
Nevada's population. Figure 4-1 clearly depicts a breakdown in the correlation that at one point existed
between these datasets and total sector emissions during the recession.
21
This method can result in under/overestimating emissions as the disaggregations for the original region is based
on comparisons of population and GDP amongst the state's in the group.
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