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( ethanol, butanol), chemically stored electricity(batteries and fuel cells), hydrogen, non-fossil methane, non-fossil natural gas, vegetable oil and other biomasssources.
The main purpose of fuel is to store
energyin a form that is stable and can be easily transported from the place of production to the end user which helps in many ways such as transportation. Almost all fuels are Chemicalfuels, that store chemical potential energy. The end user is then able to consume the fuel at will, and release energy, usually in the form of heat for a variety of applications, such as powering an engineor heatinga building, such as a home.
Factors increasing demand for alternative fuels
In 2007, there were 1.8 million alternative fuel vehicles sold in the United States, indicating an increasing popularity of alternative fuels. [ [http://www.autobloggreen.com/2008/04/05/auto-alliance-1-8-million-alternative-fuel-vehicles-sold-in-200/ Auto Alliance: 1.8 million alternative fuel vehicles sold in 2007] ] 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 gasconcentrations" [ [http://www.ipcc.ch/SPM2feb07.pdf] ] . Since burning fossil fuelsare known to increase greenhouse gas concentrations in the atmosphere, they are a likely contributor to global warming.
Other concerns which have fueled demand revolve around the concept of
Peak oil, which predicts rising fuel costs as production rates of petroleumenters 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 developmentfor a general discussion)
In an attempt to increase demand for alternative fuels in the US, the
IRSbegan allowing taxpayers to claim a special tax credit for using alternative fuels, known as the Alternative Fuel Vehicle Refueling Property Credit. The definition used for alternative fuel under this credit is: Any fuel containing at least 85 percent of one or more of ethanol, natural gas, compressed natural gas, liquefied natural gas, liquefied petroleum gas, or hydrogen; or any mixture which consists of two or more of biodiesel, diesel fuel, or kerosene, and at least 20% of which consists of biodiesel. [ [http://www.irs.gov/pub/irs-pdf/f8911.pdf IRS Form 8911] for 2007]
The production of alternative fuels can have widespread effects. For example, the production of corn-based
ethanolhas created an increased demand for the feed stock, causing rising prices in almost everything made from corn. [ [http://e85.whipnet.net/e85.price/corn.rush.html E85 | We need more Corn! ] ] However, in a competitive free market, an increased supply of ethanol reduces the demand for conventional fuels, and thus lowers fuel prices. The ethanol industry enables agricultural surpluses to be used to mitigate fuel shortages.
Renewable energyis energy from renewable resources such as wind power, solar power, tidal power, geothermal power, hydropower, or thermal depolymerization. Biofuels are also considered renewable if their source is sustainable. Although renewable energy is used mostly to generate electricity, it is often assumed that some form of renewable energy or at least sustainable energyis used to create alternative fuels. Several alternative fuels however, such as nuclear fuel and alternative fossil fuels, are made from non-sustainable sources, and fuels for Hydrogen fuel cells and air engines can be created by non-sustainable means as well. Such non-sustainable fuels are offered as alternatives usually because they cause less pollution at the point of use.
Biomass in the energy production industry refers to living and recently dead
biological materialwhich can be used as fuel or for industrial production. Biomass is grown from several plants, including miscanthus, switchgrass, hemp, corn, poplar, willow[cite conference | author = T.A. Volk, L.P. Abrahamson, E.H. White, E. Neuhauser, E. Gray, C. Demeter, C. Lindsey, J. Jarnefeld, D.J. Aneshansley, R. Pellerin and S. Edick | title = Developing a Willow Biomass Crop Enterprise for Bioenergy and Bioproducts in the United States | booktitle = Proceedings of Bioenergy 2000 | publisher = North East Regional Biomass Program| date = October 15-19, 2000 | location = Adam's MarkHotel, Buffalo, New York, USA | URL = http://bioenergy.ornl.gov/papers/bioen00/volk.html | accessdate = 2006-12-16 | id = OCLC|45275154 ] , sugarcane, oil palm( palm oil), and algae oil.
Most commonly, biomass refers to plant matter grown for use as
biofuel, but it also includes plant or animal matter used for production of fibres, chemicals or heat. Biomass may also include biodegradable wastes that can be burnt as fuel. It excludes organic materialwhich has been transformed by geological processes into substances such as coalor petroleum.
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,
woodand 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).Fact|date=July 2008 Ethanol can be mass-produced by fermentation of the starch or sugar in a wide variety of crops (bio-ethanol), or by hydration of ethylenefrom petroleum and other sources.
There has been considerable debate about how useful bio-ethanol will be in replacing fossil fuels in vehicles. Concerns relate to the large amount of arable land required for crops, [ [http://www.efrc.com/manage/authincludes/article_uploads/Deforestation%20diesel1.pdf Deforestation diesel – the madness of biofuel] ] as well as the energy and pollution balance from the ethanol production cycle . [Youngquist, W. Geodestinies, National Book company, Portland, OR, 499p.] [ [http://www.oilcrash.com/articles/pf_bio.htm The dirty truth about biofuels] ] Recent developments with cellulosic ethanol production and commercialization may allay some of these concerns. [ [http://news.bbc.co.uk/2/hi/science/nature/5353118.stm Biofuels look to the next generation] ]
Methanol as a fuel also has several disadvantages.
Hydrogenas a fuel has been suggested to have the capability to create a hydrogen economy. However, there is no accessible natural reserve of uncombined hydrogen, since what little there is resides in Earth's outer atmosphere. Therefore, hydrogen for use as fuel must first be produced using another energy source, making it a means to transport energy, rather than an energy source, similar to a rechargeable battery. One existing method of hydrogen production is steam methane reformation; however, this method requires methane (most commonly available as natural gas), which raises sustainability concerns. Another method of hydrogen production is through electrolysis of water, in which electricity generated from any source can be used. Photoelectrolysis, biohydrogen, and biomass or coal gasificationhave also been proposed as means to produce hydrogen.
According to the majority of energy experts and researchers, hydrogen is currently impractical as an alternative to fossil-based liquid fuels. While hydrogen has a very high energy content by weight, it has a very low energy content by volume, making it very challenging to store in average sized vehicles. Hydrogen can be stored as
compressed hydrogen, as cryogenic liquid hydrogen, or in compounds containing hydrogen which must undergo a chemical change to release the gas such as metal hydrides. [ [http://www.bnl.gov/est/erd/hydrogenStorage/ Hydrogen storage in metal hydrides] Brookhaven National Laboratory] However, because of the lower volumetric energy, hydrogen gas tanks would need to be 2-3 times as large for compressed hydrogen storageas conventional gasoline tanks.
The production of the fuel cells for hydrogen cars are often expensive as most designs require large amounts of platinum as a catalyst.Fact|date=September 2008 Other concerns involve the fragility of the fuel cell and their tendency to freeze, the flammability of hydrogen, and vehicle and infrastructure production costs.Fact|date=September 2008 Currently, due to efficiencies of scale, it is more efficient to burn fossil fuels to produce hydrogen than to burn oil directly in car engines.Fact|date=September 2008
Air engineis an emission-free piston engine using compressed air as fuel. Unlike hydrogen, compressed airis about 10x cheaper than fossil oil, making it an economically attractive alternative (hydrogen is about 10x more expensive than oil or 100x more expensive than compressed air). The air engine has also broken most barriers (storage of the energy, range, ....). Models exist which can achieve speeds over 35mph with air alone, but at least one company claims it will produce an "Air Car" hybrid by 2010 which will be able to achieve over 100mpg with a top speed of 96mph. [ [http://www.popularmechanics.com/automotive/new_cars/4251491.html Air-Powered Car Coming to U.S. in 2009 to 2010 at Sub-$18,000, Could Hit 1000-Mile Range] ]
Alternative fossil fuels
Compressed natural gas(CNG) is a cleaner burning alternative to conventional petroleum automobilefuels. The energy efficiency is generally equal to that of gasoline engines, but lower compared with modern diesel engines. CNG vehicles require a greater amount of space for fuel storage than conventional gasoline power vehicles because CNG takes up more space for each GGE (Gallon of Gas Equivalent). Almost any existing gasoline car can be turned into a bi-fuel (gasoline/CNG) car. However, natural gas is a finite resource like all fossil fuels, and production is expected to peak soon after oil does. [ [http://www.raisethehammer.org/index.asp?id=460 Peak Natural Gas is On the Way] ]
There are large but finite
coalreserves which may increasingly be used as a fuel source during oil depletion. The Fischer-Tropsch processconverts carbon dioxide, carbon monoxideinto heavier hydrocarbons, including "synthetic" oil. It is used today in South Africato produce most of that country's dieselfrom coal. The Karrick processis an improved methodology for coal liquefaction, with higher efficiency. Since there are large but finite coal reserves in the world, this technology could be used as an interim transportation fuel if conventional oil were to become scarce. There are several companies developing the process to enable practical exploitation of so-called stranded gas reserves, those reserves which are impractical to exploit with conventional gas pipelines and LNGtechnology. Methane hydrateis a form of natural gas. This substance consists of methane molecules trapped within the crystalline structure of water ice and is found in deposits under ocean sediments or within continental sedimentary rock formations. It is estimated that the global inventory of methane hydrate may equal as much as 10x the amount of natural gas. With current technology, most gas hydrate deposits are unlikely to be commercially exploited as an energy source. In addition, the combustion of methane releases the greenhouse gas carbon dioxideinto the atmosphere. Methaneis also a greenhouse gas. In other respects methane hydrate has the same problems of fossil fuel.Fact|date=September 2008
Nuclear power is any
nuclear technologydesigned to extract usable energy from atomic nucleivia controlled nuclear reactions. The most common method today is through nuclear fission, though other methods include nuclear fusionand radioactive decay. All current methods involve heating a working fluid such as water, which is then converted into mechanical work for the purpose of generating electricity or propulsion. Today, more than 15% of the world's electricity comes from nuclear power, over 150 nuclear-powered naval vessels have been built, and a few radioisotope rockets have been produced.
Fission reactors use the U-235
isotopeof uraniumfor fuel. While uranium is a fairly common element, the U-235 isotope is relatively rare. Using current reactor technology and current usage levels, and assuming an economical price of extraction, there is approximately 50 years of viable uranium available. Alternative reactor technologies exist which can use the much more common U-238 isotope, but these breeder reactors have technical issues (resulting from the higher levels of heat and radiation produced) to overcome before they can be employed economically.
Since automobiles and trucks consume a great deal of the total energy budget of developed countries, widespread
electric vehiclestechnology would be required to convert the energy generated from nuclear power to transportation.
radioactive wastestorage problems of nuclear power have not been solved, although on-site spent fuel storage in casks has allowed power plants to make room in their spent fuel pools. Today, the only industrial solution lies with storage in underground repositories. There are widespread public concerns about the health-risks, security risks and radioactive waste disposal problems of nuclear materials.
* [http://www.eere.energy.gov/afdc/altfuel/altfuels.html Alternative Fuels Data Center (U.S. DOE)]
* [http://www.alternative-fuels.com.au/ Alternative Fuels Information Centre (Victorian Government)]
* [http://www.naftc.wvu.edu Alternative Fuel Vehicle Training] : National Alternative Fuels Training Consortium, West Virginia University U.S.
* [http://eere.energy.gov/cleancities/ Clean Cities Program] : U.S. DOE program encouraging alternative fuel use
* [http://www.iata.org/pressroom/facts_figures/fact_sheets/alt_fuels.htm International Air Transport Association] overview of alternative aviation fuels
* [http://sciencedaily.com/news/matter_energy/alternative_fuels/ ScienceDaily - Research in Alternative Fuels] : Latest research news on alternative fuels
* [http://www.energyquest.ca.gov/transportation/electric.html Student's Guide to Alternative Fuel (
California Energy Commission)]
* [http://greenfleet.info Sustainable Green Fleets] : EU-sponsored dissemination project for alternatively propelled cars and alternative fuels
* [http://popularmechanics.com/science/earth/2690341.html?page=1&c=y Pop. Mechanics: Crunching the numbers on alternative fuels]
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