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| Contribution of each metric to the FCI Success and VMT-FE Success scenarios. Credit: ACS, Melaina and Webster. Click to enlarge. |
Aggressive near-term actions are necessary in three areas—vehicle miles traveled
(VMT), vehicle fuel economy (FE), and fuel carbon intensity (FCI)—in order to achieve a “fair share” reduction within the light-duty-vehicle sector toward meeting US goals of an 83%
reduction in greenhouse gas emissions below 2005 levels by 2050, according to a new study by a team at the National Renewable Energy Laboratory (NREL).
In their study, Marc Melaina and Karen Webster developed scenarios based on different degrees of success for each of those metrics, with a focus on providing perspective on the role of FCI in achieving the 2050 GHG reduction goal for light-duty vehicles (LDVs). They used two generic scenarios demonstrate the role of FCI in meeting the 2050 goal:
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Deep reductions in FCI to compensate for relatively modest FE
improvements and VMT reductions; and -
Optimistic improvements in FE, relatively large reductions in
VMT and less aggressive FCI reductions.
They then expanded each generic scenario into three illustrative scenarios to explore the theoretical implications of meeting the 2050 goal by relying exclusively on biofuels and hybrid vehicles; biofuels and plug-in hybrid vehicles; or
hydrogen fuel cell electric vehicles.
The less-aggressive FE and VMT improvements
in the FCI Success scenario require FCI to drop to 22.4
gCO2e/MJ by 2050—a 77% reduction below the baseline. In the
VMT-FE Success scenario, an average of 35 gCO2e/MJ is required
by 2050—a 65% reduction. These scenarios illustrate that even
with significant success in controlling VMT growth and improving
FE, deep reductions in FCI are still required to achieve the
2050 goal, the authors conclude.
Significant progress would be required
in all three areas, VMT, FE and FCI, and the progress would have
to begin soon and increase rapidly. If balanced to meet an overall
GHG reduction goal, sufficiently aggressive policy goals would
result in the following deviations from the baseline scenario in
2050: a 9-21% reduction in VMT (down to 4000-4700 billion
miles per year), a 100-340% increase in new LDV FE (up to
65-110 mpgge), and a 65-77% reduction in FCI (down to 22-
35 gCO2e/MJ).
These ranges allow little room for successes in
one area to compensate for shortcomings in another; the realm of
feasible scenarios does not include business as usual trends for
any of the three metrics. Our analysis does not address the
relative cost effectiveness of different GHG reduction options,
partly due to the large uncertainties out to 2050. However, the
combination of stringent goals and cost uncertainties suggests
adoption of a broad portfolio of reduction options to increase the
probability of meeting each goal cost effectively.—Melaina and Webster
Resources
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M. Melaina, K. Webster (2011) Role of Fuel Carbon Intensity in Achieving 2050 Greenhouse Gas Reduction Goals within the Light-Duty Vehicle Sector. Environmental Science & Technology doi: 10.1021/es1037707