Transportation's Role in Reducing U.S. Greenhouse Gas Emissions ...

Transportation's Role in Reducing U.S. Greenhouse Gas Emissions: Volume 1
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2.4 PROJECTED GROWTH OF TRANSPORTATION
GREENHOUSE GAS EMISSIONS
Based on the Energy Information Administration’s (EIA) Annual Energy
Outlook (AEO), projections show little growth in GHG emissions from
transportation in the coming decades—with total GHG emissions growing only
0.7 percent between 2007 and 2030, as shown in Figure 2.15. 58 CO2 emissions
alone from transportation are expected to grow 1.8 percent, slower than the 3.5
percent growth projected for the economy as a whole. 59
According to these projections, the modes show very different rates of growth in
emissions, as shown in Table 2.3. Despite a 42 percent increase in VMT over the
period, light-duty vehicle GHG emissions are projected to decline nearly 12
percent, in response to expected increases in fuel economy from corporate
average fuel economy (CAFE) regulations, advanced technologies, and
alternative fuels. 60 Freight trucks, on the other hand, show a projected 20 percent
increase in emissions, even though freight truck VMT grows at a similar rate to
light-duty vehicles. Domestic aviation also shows significant projected growth,
with emissions climbing 27 percent. As a result, domestic aviation’s share of
total transportation emissions is expected to grow from 9 percent to more than 11
percent over this period. Although the share of emissions from light-duty
vehicles is projected to decrease, they would still account for nearly one-half of
transportation CO2 emissions.
These projections are subject to a number of uncertainties: economic growth,
population growth, future fuel prices, and expected changes in the future mix of
vehicles and fuels. The AEO projections are particularly sensitive to the assumed
rate of growth in VMT, because on-road vehicles account for more than threequarters
of transportation GHG emissions. Higher or lower VMT projections
will significantly change the projections of total GHG emissions from
58 Based on EIA AEO 2009 April Update, Reference case. CO2 numbers were taken
directly from AEO for all modes. CH4, N20, and HFCs were calculated using scaling
factors developed from reported shares for each gas from the U.S. Inventory of
Greenhouse Gas Emissions and Sinks 1990-2006 (U.S. EPA, 2008), as well as trends in CH4
and N20 emissions. HFC emissions were assumed to remain a constant share of modal
emissions.
59 Energy Information Administration. Annual Energy Outlook 2009 April Update, as
cited.
60 In the AEO 2009 reference case, ethanol GHG emissions are assumed to be net zero in
the transportation sector (direct emissions are offset by the growing of the feedstock).
The emissions of ethanol production and harvesting are included in the industrial
sector.