Switching vehicle fuels is another way to green your fleet. Biodiesel, electricity, ethanol, natural gas and propane are alternatives to traditional petroleum-based fuels. The alternative fuels have different advantages and disadvantages as well as varying degrees of applicability to different applications.

Use Ethanol

Any vehicle can use low levels of alcohol. In order to use higher blends, though, changes must be made to vehicles to handle the chemical properties of ethanol. These vehicles are referred to as flex fuel vehicles or FFVs. FFVs can operate on straight gasoline, the gasoline-ethanol mix known as E85 or any combination of the two. FFVs are the same as conventional vehicles with a few modifications made to the fuel system. This includes a sensor in the fuel delivery system that detects the amount of ethanol in the fuel and makes adjustments to the engine.

Because ethanol has less energy per unit volume than gasoline, FFVs get less miles per gallon (mpg) of E85 than conventional vehicles running on gasoline. Estimates range from 10-25% difference in mpg using E85. Keep in mind, however, that there are still petroleum reductions when using E85 even with the mpg loss because ethanol makes up most of the liquid fuel and ethanol involves less petroleum use over its life-cycle than gasoline.

Use Biodiesel

Biodiesel can be made from a variety of virgin vegetable oils as well as waste vegetable oils from cooking operations and animal fat. Soy oil is the most common feedstock in the US at this time. Any level of biodiesel, from 1 to 100 percent, can be used in diesel engines although care must be taken with high-level blends in cold weather and in some older engines. The most common biodiesel blend in use today is B20 (20 % biodiesel and 80% petro-diesel). Other commonly available blends are B50 and B99. Biodiesel is the only alternative fuel to have completed EPA's Tier I and Tier II health effects testing under the Clean Air Act. Biodiesel has lower emissions of virtually all important air emissions (carbon dioxide, hydrocarbons, particulate matter, etc.) than petro-diesel. EPA released a study showing that biodiesel blends had slightly higher NOx emission levels than petro-diesel. Newer analyses from the National Renewable Energy Laboratory (NREL) using more real-world conditions have shown slight increases and decreases of NOx emissions for biodiesel blends. NREL's latest assessment of the situation is that the biodiesel-NOx relationship is not entirely clear at this time but not likely to be significantly positive or negative.

Use Natural Gas

Natural gas is another alternative to petroleum-based fuels. Unfortunately, the selection of compressed natural gas (CNG) light-duty vehicles is extremely limited. The only CNG light-duty vehicles available at the time this guide was written is the Honda Civic. Details on this vehicles are provided in Table A-2 of Appendix A. Since CNG refueling infrastructure is limited, agencies may want to consider the Phill device, which can be installed at a home or office and fuels a vehicle overnight. Some companies are attempting to address the limited availability of CNG vehicles by upfitting conventional vehicles. Currently, there are no upfitters in Washington although negotiations are in the works. Keep an eye on the Puget Sound Clean Cities Coalition’s website for news on upfitters in the region. The outlook is somewhat brighter for medium- and heavy-duty vehicles. A number of companies make natural gas-fueled engines for these vehicles. These engines emit dramatically fewer particulate emissions than diesel engines although this gap will be narrowed as 2007 and 2010 diesel engines come onto the market. The higher prices that will go along with these new diesel engines may mean that natural gas engines become an attractive alternative for economic reasons. Natural gas, or more accurately methane, may come from renewable sources, such as wastewater treatment plants or anaerobic digesters. This form of fuel is often called bio-methane. Using this fuel increases the “greenness” of natural gas as a vehicle fuel.

Electricity, Propane and Future Fuels

Other alternative fuels are electricity and propane although neither is currently used to any substantial degree in the Pacific Northwest. Use the provided links for details on the applicability and benefits of these alternative fuels. Potential future green fuels include biomass-to-liquid fuels (second generation biofuels rather than biodiesel and ethanol), gas-to-liquid or Fischer-Tropsch fuels, hydrogen/CNG (HCNG) blends and hydrogen although how green these fuels ultimately are will depend on the feedstocks and production processes used. Electricity may be considered a future fuel as well since plug-in hybrid vehicles are emerging and battery electric vehicles appear to be in the midst of a comeback. As of the writing of this guide, none of these fuels are very practical for area fleets (with the limited exception of electricity in neighborhood and low speed electric vehicles), but circumstances may change so it is worthwhile to be aware of them and track future developments.