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

Transportation’s Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
Table 2.1 Potential Alternative Fuel Applications by Mode
Ethanol
Biodiesel
Hydrogen
Electricity
LPG
Synthetic Fuels
Natural Gas
2-6
On-Road Rail Marine Aviation
Alternative Aviation Fuels n/a n/a n/a
= Little experience or potential; = Some experience and potential; = Significant experience and potential.
• Ethanol (Section 2.2) – There are many renewable feedstocks that can be used to
produce ethanol. Blends of gasoline with up to 10 percent ethanol are commonly
utilized by existing gasoline vehicles, while blends between 10 percent (E10) and 85
percent (E85) ethanol require flex-fuel vehicles (FFV). Flex-fuel systems can operate on
fuel blends from 0 to 85 percent ethanol, and are available for a number of light-duty
vehicles. Heavy-duty transit buses designed to operate exclusively on E94 with 6
percent additives have been demonstrated in Europe but currently are not available in
the United States.
• Biodiesel (Section 2.3) – Biodiesel is an alternative fuel that can be produced from
renewable feedstock or waste oils and greases. There also is some long-term potential
for algae as a biodiesel feedstock. Blends with up to 20 percent biodiesel content with
the remainder conventional diesel (B20) can be used in most diesel on-road vehicles
without modification, although higher percentage blends may be used with minor
changes to fittings and other vehicle components. Biodiesel also has the potential for
use in rail and marine applications, but has not been extensively tested in railroad
engines or larger marine vessels.
• Natural Gas (Section 2.4) – For on-road vehicles, liquefied natural gas (LNG) is
primarily an option for medium- and heavy-duty trucks and transit buses, while
compressed natural gas (CNG) has been used in both light and heavy applications.
Light-duty natural gas vehicles are commonly converted from conventional gasoline
vehicles, and may be capable of operating on either fuel (bifuel configuration), or