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

Feasibility
Transportations Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
One often-cited barrier to widespread acceptance of light-duty diesels in the United States
is their reputation as loud, inconvenient to fuel, slow, and malodorous. These attitudes
are changing with time, as noise, odor, and performance problems have largely been
eliminated, and diesel is now being marketed as an environmentally friendly (in terms of
GHG reduction) alternative to conventional vehicles. The increased cost of the diesel
engine also is a deterrent, and extended periods like those of late in which diesel fuel is
priced higher than gasoline exacerbate cost concerns.
Motorists also have expressed reservations regarding access to diesel fuel. In one survey
46 percent of motorists were concerned about fuel availability, and only 35 percent felt
that fuel availability was adequate (Greene et al., 2004). Similar concerns may be held
regarding the limited number of diesel makes and models currently offered for sale in the
U.S. Nevertheless, diesel fuel currently is offered for sale at over 100,000 locations in the
U.S., so concerns about access may be more related to perception than actual availability. 18
Other barriers to diesel market expansion concern the advanced emissions reduction
technologies used to meet current LDV emission standards. In addition to the incremental
costs, widespread use of selective catalytic reduction (SCR) after treatment requires the
addition of a small on-board reluctant tank, in addition to operator education regarding
reductant handling and regular replacement. Tank refilling intervals for LDVs are
expected to be about as frequent as oil changes (U.S. DOE, 2009a). Some infrastructure
development also will be required for reductant distribution and storage. In addition, in
order to meet emissions requirements, vehicles may be designed to be inoperable when
the reductant runs out. As such, reliability concerns could limit the acceptance of this
technology. There also are concerns over the longevity of new components for SCR as
well as exhaust gas recirculation (EGR) coolers and diesel particulate filter (DPF) units.
Increased demand for diesel fuel itself poses its own concerns. There may be a limit to
increasing the proportion of diesel versus gasoline that is refined from a fixed amount of
crude oil. As that limit is neared, differences in gasoline and diesel fuel prices would be
expected to change, limiting the market share increase of diesel fuel (Leister, 2008). In
addition, substantial investment may be needed to expand current diesel refining capacity
to accommodate production increases.
18 NGA, 2008.
3-39