Alternative Fuels

Diesel Fuel

Description

Diesel fuel and heavy duty diesel engines have been widely used in the transportation sector. All highway diesel fuel now requires a reduction in the sulfur content of the fuel to 15 parts-per-million (ppm). Diesel fuel is derived from petroleum. It is composed of about 75% saturated hydrocarbons, and 25% aromatic hydrocarbons.

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Biodiesel

Description Biodiesel is a renewable fuel that is manufactured from domestically produced oils such as soybean oil, recycled cooking oils, or animal fats.  The most common biodiesel blend is B20 (20% biodiesel and 80% diesel). Other blends such as B5 or B2 are used as well, but in a limited form.

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Hybrid-Electric Propulsion

Description Hybrid-electric buses are powered by a combination of an engine with an electric motor and energy storage system.  The engine may work with the motor with both providing power directly to the wheels (parallel hybrid), or the engine may be used only to operate an electric generator while an electric motor provides all the power to the wheels (series hybrid).  Hybrid buses increase fuel economy by using the electric motor as a generator to slow the bus, capturing and re-using braking energy.  Hybrids also allow the engine to operate more efficiently.  In the last 5-10 years, several hybrid-electric bus models have been commercialized.  Most hybrid buses are diesel-electric (and could operate on biodiesel), however a small but increasing number are gasoline-electric.  

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Natural Gas

Description Natural gas comes in two forms: compressed (CNG) and liquefied (LNG).  If the gas is compressed, it typically comes through a utility pipeline.  If the gas is liquefied, it is typically delivered by truck.  Most of the natural gas transit vehicles in the U.S. use CNG. Natural gas vehicles are clean burning and produce significantly fewer harmful emissions than gasoline or diesel; the emissions characteristics between CNG and LNG are the same.  

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Fuel Cell Power

Description Fuel cells produce electricity continuously and directly, through a chemical reaction. Individual fuel cells are combined into “fuel cell stacks” to provide sufficient power in a single circuit.  There are currently several different types of fuel cells under development, which can run on a variety of fuels.  Hydrogen fueled Proton Exchange Membrane (PEM) Fuel cells are the most common in transportation applications. Hydrogen and ambient oxygen are fed into opposite sides of the fuel cell, separated by a membrane (the PEM), forcing a flow of electrons through an attached circuit to complete the reaction of hydrogen and oxygen into water.

PEM FUEL CELL Electrical Currents of Anode, Electrolye and Cathode depicting fuel in and excess fuel out. Air in water and heat out.

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Alternative Fuels and Propulsion Vehicle Incentives

Overview

 

Many Federal and State incentives and laws are designed to encourage the purchase of alternative fuel vehicles.  Federal incentives range from tax credits to grant programs.  Transit agencies purchasing new qualified alternative fuel vehicles will likely be eligible for several incentive programs.  A selection of major programs is included below, along with links to other sources of information.  Transit agencies should consult the provided IRS, EPA and Department of Energy sites for complete lists of incentives.

The major FTA administered incentive program is the Clean Fuel Grant Program.  This program (Section 5308, U.S.C. 49) was developed to assist non-attainment and maintenance areas in achieving or maintaining the National Ambient Air Quality Standards for ozone and carbon monoxide (CO) and to support emerging clean fuel and advanced propulsion technologies for transit buses.  To date, the Clean Fuel Grant Program has not been provided discretionary funding.

Links and Resources

Federal Transit Administration:

Environmental Protection Agency:

Department of Energy:

Internal Revenue Service:

Related Reports

Contact Information

For additional information about the Clean Fuels Grant Program, contact the FTA Office of Program Management: (202) 366-2053.

For more information about clean fuels in the transit industry, contact our Office of Research, Demonstration and Innovation at (202) 366-4052.