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

Transportation’s Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
Table 2.7 Life-Cycle Emissions for Liquid Petroleum Gas versus
Conventional Gasoline
Pollutant Change in Emissions versus Gasoline
VOC -35%
CO 0%
NOx -14%
PM10
PM2.5
-47%
-38%
SOx -14%
Feasibility
LPG is generally regarded as an exceptionally safe transportation fuel. LPG has the lowest
flammability range of all alternative fuels, and LPG tanks are 20 times more puncture
resistant than gasoline tanks. Additionally, an odorant, ethyl mercaptan, is typically
added to quickly identify tank leaks (AFDC, 2009a). For marine vessel applications, there
is a safety concern because LPG is denser than air, and it tends to accumulate in ship hulls
in concentrations that could be explosive. There is a similar concern for LPG vehicles in
enclosed spaces, which may require additional ventilation systems to avoid pooling of
vapors.
While there is a range penalty associated with dedicated LPG vehicles due to the fuel’s
lower energy density compared to gasoline (~20 percent), increasing tank volumes can be
used to offset this limitation to some degree. Vehicle performance is similar to comparable
conventional vehicles, while maintenance costs and engine life may be improved due to
LPG’s clean burning properties (AFDC, 2009a).
Because LPG already is used extensively around the country for numerous purposes, the
infrastructure for bulk production, storage, and distribution already is in place.
Infrastructure costs related to expanding LPG’s use as a transportation fuel would thus
primarily be related to expanding the distribution network by converting existing gas
stations and building new LPG stations. The conversion from a gas station to an LPG
station is straightforward, only requiring the installation of a tank, pump, and metering
equipment.
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