Alternative fuels, also known as non-conventional fuels, are any materials or substances that can be used as a fuel, other than conventional fuels. Conventional fuels include: fossil fuels (petroleum (oil), coal, propane, and natural gas), and nuclear materials such as uranium.Some well known alternative fuels include biodiesel, bioalcohol (methanol, ethanol, butanol), chemically stored electricity (batteries and fuel cells), hydrogen, non-fossil methane, non-fossil natural gas, vegetable oil and other biomass sourcesIn 2007, there were 1.8 million alternative fuel vehicles sold in the United States, indicating an increasing popularity of alternative fuels.[1] There is growing perceived economic and political need for the development of alternative fuel sources. This is due to general environmental, economic, and geopolitical concerns of sustainability.The major environmental concern, according to an IPCC report, is that "Most of the observed increase in globally averaged temperatures since the mid-20th century is due to the observed increase in anthropogenic greenhouse gas concentrations" [2]. Since burning fossil fuels are known to increase greenhouse gas concentrations in the atmosphere, they are a likely contributor to global warming.ther concerns which have fueled demand revolve around the concept of Peak oil, which predicts rising fuel costs as production rates of petroleum enters a terminal decline. According to the Hubbert peak theory, when the production levels peak, demand for oil will exceed supply and without proper mitigation this gap will continue to grow as production drops, which could cause a major energy crisis.Lastly, the majority of the known petroleum reserves are located in the middle east. There is general concern that worldwide fuel shortages could intensify the unrest that exists in the region, leading to further conflict and war. (See future energy development for a general discussion)Methanol and ethanol are typically not primary sources of energy; however, they are convenient fuels for storing and transporting energy. These alcohols can be used in internal combustion engines such as flexible fuel vehicles with minor modifications.Methanol can be produced from a wide variety of sources including fossil fuels, but also agricultural products and municipal waste, wood and varied biomass. More importantly, it can also be made from chemical recycling of carbon dioxide (such as from the CO2 rich flue gases of fossil fuel burning power plants or exhaust of cement and other factories, of even atmospheric CO2).[citation needed] Ethanol can be mass-produced by fermentation of the starch or sugar in a wide variety of crops (bio-ethanol), or by hydration of ethylene from petroleum and other sources.
