Propane, also known as liquefied petroleum gas (LPG or LP-gas), or autogas in Europe, is a three-carbon alkane gas (C3H8). Stored under pressure inside a tank, propane turns into a colorless, odorless liquid. As pressure is released, the liquid propane vaporizes and turns into gas that is used for combustion. An odorant, ethyl mercaptan, is added for leak detection. Propane has a high octane rating and excellent properties for spark-ignited internal combustion engines. It is non-toxic and presents no threat to soil, surface water, or groundwater.
The interest in propane (also known as liquefied petroleum gas or LPG) as an alternative transportation fuel stems mainly from its domestic availability, high energy density, and clean-burning qualities. It is the most commonly used alternative transportation fuel and the third most used vehicle fuel, behind gasoline and diesel. Propane is considered an alternative fuel under the Energy Policy Act of 1992.
No light-duty propane vehicles are available for sale by automotive original equipment manufacturers (OEMs). However, Roush Industries converts Ford F150 pickup trucks to dedicated propane fuel use to meet OEM-like standards and has plans to convert F250 and F350 pickups to propane use. Other certified installers can economically and reliably retrofit many light-duty vehicles for propane operation. Propane engines and fueling systems are also available for medium- and heavy-duty vehicles such as school buses and street sweepers, including some from OEMs.
Conversions in the United States require U.S. Environmental Protection Agency (EPA) approval and a licensed propane conversion technician. The average cost of conversion of a light-duty vehicle from gasoline to dedicated propane fuel ranges from $4,000 to $12,000. The upfront costs to convert fleet vehicles to propane can be offset by lower operating and maintenance costs over the lifespan of the vehicles. Conversion to a dedicated propane or bi-fuel propane vehicle can be attractive when fueling infrastructure is in place and volume fuel discounts are available. The payback period depends on the average distance traveled by these fleet vehicles. Fleet vehicles typically are high-mileage, high fuel consumption vehicles operating in a limited area, so the payback period on propane fleet vehicles can be very reasonable.
School districts in Dallas and Denton, Texas, and Portland, Oregon, rely on propane school buses. Dallas County operates 500 propane buses. In 2007, Blue Bird Corporation introduced the Vision Propane model, the first propane bus from a major manufacturer since 2002. It features CleanFUEL USA’s Liquid Propane Injection (LPI) system. In Virginia, Gloucester County Public Schools operates 5 Blue Bird propane buses.
Ethanol is a renewable fuel made from various plant materials, which collectively are called “biomass.” Ethanol contains the same chemical compound (C2H5OH) found in alcoholic beverages. Nearly half of U.S. gasoline contains ethanol in a low-level blend to oxygenate the fuel and reduce air pollution. Ethanol is also increasingly available in E85, an alternative fuel that can be used in flexible fuel vehicles. Studies have estimated that ethanol and other biofuels could replace 30% or more of U.S. gasoline demand by 2030. Ethanol is a renewable, largely domestic fuel. Whether used in low-level blends, such as E10 (10% ethanol, 90% gasoline), or in E85 (85% ethanol, 15% gasoline), ethanol helps reduce imported oil and greenhouse gas emissions. Its use also supports the U.S. agricultural sector.
Low-level ethanol blends such as E10 already constitute much of the gasoline sold in the United States. Low-level blends require no special fueling equipment and can be used in any gasoline-powered vehicle. E85 fueling equipment is slightly different than petroleum fueling equipment, but the costs are similar. In some cases, it is possible to convert existing petroleum equipment to handle E85. FFVs designed to run on E85 are becoming more common each model year, and FFVs are typically available as standard equipment with little or no incremental cost. Also, because FFVs can be fueled with gasoline as well as E85, drivers have the flexibility to travel outside of areas served by E85 fueling stations.
Fleets throughout Virginia have instituted alternate fuel purchasing preferences, where flexible fuel vehicles are purchased when they are available and when cost differences are minimal. There are more than 3,000 flex fuel vehicles in Virginia fleets today, and more than 8 million flex fuel vehicles on the road. Fleets that are based nearby public E85 stations often educate their drivers as to the nearby flex fueling stations, or require vehicles refuel there. E85 is usually 10-15% cheaper than gasoline in Virginia. Key fleets, such as the US navy, have purchased hundreds of E85 compatible vehicles and integrated nearby E85 fueling into their fleet fueling practices.
Compressed Natural Gas
Natural gas is a mixture of hydrocarbons, predominantly methane (CH4). As delivered through the pipeline system, it also contains hydrocarbons such as ethane and propane and other gases such as nitrogen, helium, carbon dioxide, hydrogen sulfide, and water vapor. Natural gas has a high octane rating and excellent properties for spark-ignited internal combustion engines. It is non-toxic, non-corrosive, and non-carcinogenic. It presents no threat to soil, surface water, or groundwater.
The U.S. Environmental Protection Agency has called the natural gas Civic GX the cleanest internal-combustion vehicle on Earth. For more light-duty NGV options, see the NGVAmerica’s list of Available Natural Gas Vehicles and Engines (PDF 66 KB). This document lists light-, medium-, and heavy-duty natural gas vehicles and engines available directly from large original equipment manufacturers (OEMs) or via qualified system retrofitters using EPA-/CARB-certified systems from small-volume OEMs. It also provides manufacturer and retrofitter contact information. For more on retrofit NGVs, read NGVAmerica’s Frequently Asked Questions About Converting Vehicles to Operate on Natural Gas (PDF 83 KB) for the most recent list of available heavy-duty natural gas engines. These engines can be used for various applications, such as transit buses, school buses, and refuse trucks. Contact the engine manufacturers (see contact information in Available Natural Gas Vehicles and Engines) to find out which vehicles feature their engines. Alternatively, contact heavy-duty vehicle manufacturers to learn about the natural gas vehicles they offer. Also see the AFDC Heavy-Duty Vehicle and Engine Search.
There are several useful municipal fleet options for CNG applications. Recently, Virginia Clean Cities, along with NGVAmerica, hosted a Compelling Case for Natural Gas Workshop in Arlington, VA. Several natural gas adopters showcased their experiences. You can find all presentations at NGVAmerica’s website fueling stations and directly to end users such as large vehicle fleets. Most biodiesel distributors will deliver pure or preblended (with petroleum diesel) biodiesel depending on the customer’s preference. Currently, most users are using a blend of B5 (5% biodiesel) to B20 (20% biodiesel). These are the most readily available, cost-effective blends.
There are many good examples of biodiesel use on a fleet scale. Arlington County, VA provides a great local case study. Arlington began to use B20 in its school buses and other fleet vehicles in 2001. National Biodiesel Board keeps location maps for stations and distributors at http://biodiesel.org.
All-electric vehicles (EVs) use a battery to store the electrical energy that powers the motor. EVs are sometimes referred to as battery electric vehicles (BEVs). EV batteries are charged by plugging the vehicle into an electric power source. Although electricity production might contribute to air pollution, all-electric vehicles are considered zero-emission vehicles because their motors produce no exhaust or emissions. Because EVs use no other fuel, they help reduce petroleum consumption.
Heavy-duty vehicles are available now, and more light-duty EVs are nearing commercial availability. Although EVs are more expensive than similar conventional and hybrid vehicles, some cost can be recovered through fuel savings, a federal tax credit, or state incentives.
All-electric vehicles will have a shorter range per charge than conventional vehicles have when they fill up with gas. The custom-order, all-electric Tesla Roadster has a 220-mile range while less-expensive vehicles soon to be sold throughout Virginia are targeting a 100-mile range. According to the U.S. Department of Transportation Federal Highway Administration, 100 miles is sufficient for over 90% of all household vehicle trips in the United States.
There are many tax credits and incentives for alternative fuel usage at the federal and state level. A rundown of federal tax credits can be found here, and a rundown of state incentives can be found here.