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

Transportation’s Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
2-20
costs; however, others may reduce net ownership costs. The relative costs and benefits
will vary for each option depending on incremental vehicle costs and fuel prices.
Increased domestic fuel production will provide additional employment opportunities.
Finally, many of these options will require increased vehicle manufacturing capacity to
meet increased demand, which also will increase employment opportunities.
• Efficient System Management and Operation – Certain fuel options may affect the
management and operation of the transportation system. To the extent that access to
alternative fuels may be limited, system operation may be constrained to certain
regions or refueling locations. Such concerns will be most prevalent during transition
periods, before full build out of new infrastructure capacity.
• System Preservation – The fuel options are assumed to have negligible impact on
preservation of the existing infrastructure.
Table 2.3 Relative Life-Cycle Emissions of Alternative Fuels (Percent
Change versus Conventional Gasoline)
Conventional
Gasoline
Gaseous
Pollutant Emissions (g/mi) CNG LPG Hydrogenb Battery
Electric
Vehiclec VOC 0.316 -45% -35% -92% -91%
CO 3.817 0% 0% -98% -98%
NOx 0.379 -20% -14% -59% -11%
PM10 0.083 -9% -47% 23% 416%
PM2.5 0.036 -20% -38% 36% 220%
SOx 0.126 +11% -14% N/A 494%
Source: GREET Model Version 1.8b, with default assumptions for current vehicle technologies. Relative
emissions will vary depending upon vehicle emission controls as well as fuel extraction and
production methods. Relative emissions may change in future years as these various technologies
evolve in different ways.
b Assuming distributed natural gas reforming, the current primary production pathway; these values do not
represent future technologies or other production pathways or feedstocks. Refer to Section 2.8 for detailed
hydrogen production pathways.
c Assuming current grid-average electricity generation mix. Future scenarios will differ considerably
depending upon grid mix and when vehicles are charged. See Section 3.2.4 for a detailed analysis of
electricity dispatch impacts.