• A car loading fuelRefuelling by gasoline of the modern car image by terex from Fotolia.com
  
  Alternative fuels are derived from resources other than petroleum. Some are produced domestically, reducing the dependence on imported oil, and some are derived from renewable sources. Often, they produce less pollution than gasoline or diesel. There are mainly five alternative fuels---ethanol, biodiesel, natural gas, propane and hydrogen---currently in use in the U.S. and in other countries.
  
  

Ethanol

• Ethanol has been using as an alternative fuel source for than one decade. Ethanol is an alcohol-based fuel, derived by fermentation and distillation of corn and other crops. Also cellulosic biomass can be a source for ethanol. Cellulosic biomass derives from trees and other plants. Cellulose is the structural component of the primary cell walls of green plants and can be used to produce methane in bio gas plants. There are nearly 2,000 filling stations in the U.S. selling E 10 (gasohol) and /or E 85. The price regionally differs; it can be somewhat expensive than gasoline. E 10 is a mixture of 90 percent gasoline and 10 percent ethanol; the latter is 85 percent ethanol and 15 percent gasoline blend.
  
  Ethanol produces fewer greenhouse gases compared to conventional fuels. The performance of the car is reported the same as using petroleum derivates. E 10 is approved by all auto manufacturers, while E 85 can only be used in flex fuel vehicles. Power derived from ethanol is less, so range and performance of the car could be affected
  
  

Biodiesel

• Biodiesel is made from vegetable oils and animal fats. Biodiesel is blended with petroleum deriviates in various percentages (celled B 2, B 5, and B 20). In this case the number gives the percentage of the part of biodiesel in the blend. B2 and B5 can be used safely in all diesel engines; hence the use of a higher percentage might be possible but is not covered by some manufacturer's warranties. Biodiesel is less polluting than sole petroleum deriviates.
  
  

Natural Gas

• Natural gas is mainly methane. It is a fossil fuel. Vehicles that support a dual-fuel system can run on both natural gas and gasoline or diesel. Natural gas is cleaner and cheaper than gasoline and diesel but the availability of natural gas filling stations is not extensive throughout the United States. Natural gas produces 90 percent fewer pollutants than regular gas. One of the disadvantages is that the car needs an extra tank, which frequently reduces trunk space.
  
  

Propane

• Propane or liquefied petroleum gas (LPG) is known as a clean fossil fuel. LPG-driven vehicles produce fewer pollutants than regular gasoline. LPG trucks or cars have not been produced in the U.S. since 2004. However, gasoline and diesel cars can be retrofitted to run on LPG. LPG is stored in high-pressure fuel tanks, so separate fuel systems are needed in that case.
  
  

Hydrogen

• Although it has been under investigation for many years, hydrogen is still a source of energy that is not currently on the verge of general use. Hydrogen is still very expensive and available only in some determined locations, mostly in California. Hydrogen is a nonpollutant fuel that is absolutely friendly to the environment, and because the raw material is simple water it should be available everywhere once the process of exploitation is lined up.