In addition to gasoline, diesel, hybrid, and electric vehicles, there are several other alternative and advanced fuel vehicles on the market. These vehicles are not as common as gasoline or diesel vehicles, but they are still commercially available and important to mention as they may become more common in the future.
These fuels are often studied because they may reduce petroleum use, lower some emissions, or provide more fuel choices for drivers and fleets.
Biodiesel
Biodiesel is a fuel that can be made from vegetable oils, animal fats, or recycled cooking oil, such as used fryer oil from restaurants. It can be used in some diesel engines as an alternative to petroleum diesel.
Biodiesel is usually sold as a blend with petroleum diesel. For example:
- B20 = 20% biodiesel and 80% petroleum diesel
- B100 = 100% biodiesel
Many diesel vehicles can use lower biodiesel blends, such as B5 or B20, without major changes. Higher blends may require engine modifications or manufacturer approval.
Biodiesel is often described as a cleaner-burning fuel than petroleum diesel. It can also improve the lubricity of the fuel, which means it helps reduce friction between engine parts. Some drivers even say biodiesel exhaust smells a little like fried food.
Ethanol
Ethanol is an alcohol-based fuel with the chemical formula CH3CH2OH. In the United States, ethanol is commonly made by fermenting corn. In other countries, such as Brazil, it is often made from sugar cane.
Text description of the Ethanol image.
Ball-and-stick model of an ethanol molecule (CH3CH2OH) showing a simple organic structure composed of two carbon atoms, six hydrogen atoms, and one oxygen atom. The two carbon atoms are connected in a short chain, with an oxygen atom attached to one end and a hydrogen atom bonded to the oxygen, forming a hydroxyl group. Carbon atoms are typically shown as dark gray or black spheres, hydrogen atoms as smaller white spheres, and the oxygen atom as a red sphere.
Note: You can use your mouse to rotate and zoom in on the Iso-octane molecule.
Ethanol is blended into most gasoline sold in the United States. The most common blend is:
- E10 = 10% ethanol and 90% gasoline
Some vehicles, called flex-fuel vehicles, can use higher ethanol blends such as E85.
Because ethanol contains oxygen, it can help gasoline burn more completely in the engine. This can reduce carbon monoxide and some other pollutants.
However, ethanol contains less energy per gallon than gasoline. This means a vehicle will usually travel fewer miles on a gallon of ethanol than on a gallon of pure gasoline.
Ethanol has less energy per gallon than petroleum derived gasoline, which means you will be able to drive less miles on one gallon of ethanol versus on gallon of gasoline.
Natural Gas
As discussed earlier in the course, natural gas is a fossil fuel made mostly of methane, CH4.
Natural gas vehicles are designed to use either:
- Compressed natural gas (CNG)
- Liquefied natural gas (LNG)
CNG is stored at very high pressure, usually around 3,600 psi. LNG is natural gas that has been cooled to about -260°F so that it becomes a liquid.
Natural gas vehicles are often used in fleet applications, such as buses, delivery vehicles, and municipal vehicles. They work especially well when vehicles return to a central location each day for fueling.
Even though natural gas pipelines are common in many parts of the United States, CNG and LNG fueling stations are much less common than gasoline stations. This is one reason natural gas vehicles are often used in centrally managed fleets rather than by individual drivers.
Propane
Propane, also called liquefied petroleum gas (LPG), is another alternative transportation fuel. It is used in some fleet vehicles, school buses, delivery trucks, and service vehicles.
Propane is C3H8
Text description of the Propane image.
Ball-and-stick model of a propane molecule (C3H8) showing a straight-chain hydrocarbon structure composed of three carbon atoms and eight hydrogen atoms. The carbon atoms are connected in a short chain, with hydrogen atoms attached around the outside. Carbon atoms are typically shown as dark gray or black spheres connected by rods, while hydrogen atoms are shown as smaller white spheres. Propane is a three-carbon alkane with the molecular formula C₃H₈.
Credit: Moleview
Note: You can use your mouse to rotate and zoom in on the Iso-octane molecule.
Propane vehicles can produce lower emissions of some pollutants compared with conventional gasoline vehicles. Propane is also widely used in areas where fleet managers want a fuel that is easy to store and transport.
Like natural gas, propane is most common in fleet settings where vehicles can refuel at a central location. It is less common for personal passenger vehicles.
Hydrogen
Hydrogen is the simplest element on the periodic table with just one electron and proton. Hydrogen can also be used as transportation fuel. Some vehicles use hydrogen in a fuel cell, which produces electricity to power an electric motor. These vehicles are called fuel cell electric vehicles (FCEVs).
Hydrogen fuel cell vehicles do not burn gasoline or diesel. Instead, the fuel cell combines hydrogen with oxygen from the air to produce electricity. The main byproduct is water vapor.
Hydrogen vehicles can be refueled more quickly than many battery electric vehicles, but hydrogen fueling stations are still very limited in most areas. Because of this, hydrogen vehicles are not yet common for most drivers.