Alternative Fuels for Automobiles

Last Updated: 26 Mar 2023
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Alternative fuel, also known as non-conventional fuels, is any material or substance that can be used as a fuel, other than fossil fuels. Alternative fuels, as defined by the Energy Policy Act of 1992 (EPAct), include ethanol, natural gas, propane, hydrogen, biodiesel, electricity, methanol, and p-series fuels. Using these alternative fuels in vehicles can generally reduce harmful pollutants and exhaust emissions. Alternative fuels are designed to be cheap, non-polluting, 'infinite' sources of energy. No such fuels currently exist globally, or they would by now be rapidly replacing current fossil fuels. In the year 2000, there were about eight million vehicles around the world that ran on alternative fuels. A primary concern is that the fact that the use of conventional fuels directly contributes to the global warming crisis.

Another concern is the problem of peak oil, which predicts a rising cost of oil derived fuels caused by severe shortages of oil during an era of growing energy consumption. According to the 'peak oil' phenomenon, the demand for oil will exceed supply and this gap will continue to grow, which could cause a growing energy crisis by the year 2010 or 2020. Most of the interest in alternative fuels has focused on transportation vehicles, since this application represents 70% of petroleum consumption.

The President also proposes acceleration of the development of domestic, renewable alternatives to gasoline and diesel fuels through: $150 million for the Biofuels Initiative—a $59 million increase over FY 2006—to help develop bio-based transportation fuels such as “cellulosic ethanol” from agricultural waste products, such as wood chips, stalks, or switchgrass; $31 million to speed the development of advanced battery technology to extend the range of hybrid vehicles and make possible “plug-in” hybrids and electric cars—a 27 percent increase over FY 2006; and $289 million for the President’s Hydrogen Fuel Initiative. President Bush outlined the Advanced Energy Initiative (AEI) in pursuit of a national goal of replacing more than 75 percent of U. S. oil imports from the Middle East by 2025. Since 2001, nearly $10 billion has been invested by the Federal government to develop cleaner, cheaper and more reliable alternative energy sources.

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Ethanol can run at a much higher compression ratio without octane-boosting additives. It burns more completely because ethanol molecules contain oxygen; carbon monoxide emissions can be 80-90% lower than for fossil-fuelled engines. (Hua Lu Karlsson. 2006). However, ethanol is degrading to some plastic or rubber parts of fuel delivery systems designed to use petrol, and has 37% less energy per litre than petrol . There has been a recent revival in interest in the use of ethanol-diesel fuel blends(E-diesel) in heavy-duty vehicles as a means to reduce petroleum dependency, increase renewable fuels use, and reduce vehicle emissions. The major concern with the use of E-diesel derives from its flammability characteristics.

E-diesel blends containing 10% to 15% ethanol have the vapor pressure and flammability limits of ethanol. This means that ethanol concentrations in enclosed spaces such as fuel storage and vehicle fuel tanks are flammable over the temperature range of 13 to 42°C, typical ambient temperatures. Thus, there are increased risks of fire and explosion compared to diesel fuel, or even gasoline. Other vehicle performance-related concerns have also been raised.

These include decreased maximum power, increased incidence of fuel pump vapor lock, and reduced fuel pump and fuel injector life due to the decreased lubricity of ethanol. Ethanol can be blended directly in petrol, up to a mix of 20%, without engine modifications, though engines would need to be modified for higher blends. Ethanol-blended diesel fuels (10 to 15% ethanol) require emulsifiers and solubilisers, depending on the ethanol quality. For use of pure ethanol in diesel engines an additive (ignition improver) is needed for cold start and idling. Fuel pump adaptations may also be necessary.

Barriers to the use of ethanol in diesel fuel include limited miscibility at lower temperatures and need for minor variations in fuel delivery systems to account for the different physical properties of ethanol as compared to diesel. An increase in fuel consumption approximately equivalent to the reduction in energy content of the fuel can be expected when using ethanol-diesel blends. With ethanol percentages of 10%or less, operators have reported no noticeable differences in performance compared to running on diesel fuel. The use of E diesel is the affect of the ethanol on the lubricating properties of the fuel and the potential for fuel system wear. Additive packages that are used to formulate E diesel fuels can improve fuel lubricity and prevent abnormal fuel system wear.

The heavily promoted alcohol fuel called E85 might cut America's oil use and help support U. S. agriculture, but it's not reducing motorists' fuel bills. E85 is a blend of 85% ethanol and 15% unleaded gasoline for use in flexible fuel vehicles (FFVs). E85 is classified as an alternative fuel by the U. S. Department of Energy. A flexible-fuel vehicle (FFV) is a vehicle that can operate on any blend of ethanol up to 85%. If E85 is not available, the vehicle can operate on straight unleaded gasoline or any percentage of ethanol up to 85%. It has the highest oxygen content of any fuel available today, allowing it to burn more completely (cleaner) than conventional gasoline. E85 contains 80% less gum-forming compounds, like the olefins found in gasoline. Production and use of E85 results in a nearly 30% reduction in greenhouse gas emissions.

Methanol, also known as wood alcohol, can be used as an alternative fuel in flexible fuel vehicles that run on M85 (a blend of 85% methanol and 15% gasoline). However, it is not commonly used because automakers are no longer supplying methanol-powered vehicles. Methanol is even more corrosive and its energy per liter is 55% lower than that of petrol. Methanol can be used in internal combustion engines with minor modifications. It usually is made from natural gas, sometimes from coal, and could be made from any carbon source including CO2.

The ability to produce methanol from non-petroleum feedstocks such as coal or biomass is of interest for reducing petroleum imports. Methanol can be used to make methyl tertiary-butyl ether (MTBE), an oxygenate which is blended with gasoline to enhance octane and create cleaner burning fuel. MTBE production and use has declined because it has been found to contaminate ground water. Methanol produces a high amount of formaldehyde in emissions. In the future, methanol could possibly be the fuel of choice for providing the hydrogen necessary to power fuel cell vehicles.

Propane or liquefied petroleum gas (LPG) is also fast becoming a popular alternative fuel. It is a by-product of natural gas processing and crude oil refining. Propanol and butanol are considerably less toxic and less volatile than methanol. In particular, butanol has a high flashpoint of 35 °C, which is a benefit for fire safety. The fermentation processes to produce propanol and butanol from cellulose are fairly tricky to execute, and the Weizmann organism (Clostridium acetobutylicum) currently used to perform these conversions.

Propane vehicles can produce fewer ozone-forming emissions than vehicles powered by reformulated gasoline. There is 98% reduction in the emissions of toxics, including benzene, 1,3 butadiene, formaldehyde, and acetaldehyde, when the vehicles were running on propane rather than gasoline. The cost of a gasoline-gallon equivalent of propane is generally less than that of gasoline, so driving a propane vehicle can save money. In addition, propane is the most accessible of all alternative fuels.

Natural gas in the form of compressed natural gas (CNG) or liquefied natural gas (LNG) is fast becoming one of the most popular alternative fuels. Natural gas contains hydrocarbons such as ethane and propane; and other gases such as nitrogen, helium, carbon dioxide, hydrogen sulfide, and water vapor and is produced either from gas wells or in conjunction with crude oil production. Natural gas pollutes much less than gasoline and very little has to be done to modify an internal combustion engine. It is also clean-burning and produces significantly fewer harmful emissions than reformulated gasoline or diesel when used in natural gas vehicles.

Smog-producing gases, such as carbon monoxide and nitrogen oxides, are reduced by more than 90% and 60%, respectively and carbon dioxide, a greenhouse gas, is reduced by 30%-40%. Natural gas can either be stored onboard a vehicle as compressed natural gas (CNG) at 3,000 or 3,600 psi or as liquefied natural gas (LNG) at typically 20-150 psi. Natural gas can also be blended with hydrogen. Hydrogen (H2) will play an important role in developing sustainable transportation, because in the future it may be produced in virtually unlimited quantities using renewable resources.

Hydrogen has been used effectively in a number of internal combustion engine vehicles as pure hydrogen mixed with natural gas. In addition, hydrogen is used in a growing number of demonstration fuel cell vehicles. Hydrogen and oxygen from air fed into a proton exchange membrane (PEM) fuel cell "stack" produce enough electricity to power an electric automobile, without producing harmful emissions. Fuel cells generate electricity by electrochemically combining hydrogen and oxygen. On a life-cycle basis, they produce zero or very low emissions, depending on the source of the hydrogen.

Fuel cells are highly efficient energy-conversion devices that utilize hydrogen. But there are still many barriers to their use in vehicles, including the lack of a hydrogen distribution infrastructure, high capital costs for fuel cells and hydrogen-production technologies, and challenges related to hydrogen storage. The main difference is that batteries store electrical energy, while fuel cells generate electricity continuously as long as an external fuel source is supplied. That means their performance is not hindered by lengthy, inconvenient recharging times.

If pure hydrogen is used as the fuel source, the only products are electricity, heat and water. The solid oxide fuel cell is able to directly utilize commonly available fuels such as natural gas, liquefied petroleum gas, diesel and biogas. When operating on natural gas, carbon dioxide (CO2) emissions are reduced by up to 60 percent compared with conventional electricity generation, with practically no emissions of nitrogen oxides (NOx) and sulfur oxides (SOx). Many scientists believe that pure hydrogen, the most common element on earth, is destined to be the vehicle fuel of the future.

Hydrogen can be extracted from thousands of compounds, including natural gas, water, sugar and many petroleum products. The extraction of hydrogen requires energy, making hydrogen an energy carrier rather than an energy source. In transportation, and for many other applications, fuel cell technology is opening new doors of opportunity for hydrogen. Governments and industry around the world, are investing heavily in research and development into hydrogen fuel cells. 6. BIODIESEL Pure biodiesel is considered an alternative fuel under EPAct.

Biodiesel (fatty acid alkyl esters) is a cleaner burning diesel replacement fuel that can be manufactured from vegetable oils, animal fats, or recycled restaurant greases. Biodiesel is safe, biodegradable, and using in a conventional diesel engine substantially reduces emissions of unburned hydrocarbons, carbon monoxide, sulfates, polycyclic aromatic hydrocarbons, nitrated polycyclic aromatic hydrocarbons, and particulate matter. These reductions increase as the amount of biodiesel blended into diesel fuel increases.

The use of biodiesel decreases the solid carbon fraction of particulate matter (since the oxygen in biodiesel enables more complete combustion to CO2) and reduces the sulfate fraction (biodiesel contains less than 15 ppm sulfur), while the soluble, or hydrocarbon, fraction stays the same or increases. Therefore, biodiesel works well with emission control technologies such as diesel oxidation catalysts (which reduce the soluble fraction of diesel particulate but not the solid carbon fraction). Blends of 20% biodiesel with 80% petroleum diesel can generally be used in unmodified diesel engines.

Biodiesel can also be used in its pure form, but it may require certain engine modifications to avoid maintenance and performance problems and may not be suitable for wintertime use. Just like petroleum diesel, biodiesel operates in compression-ignition engines. Higher blends, even pure biodiesel (100% biodiesel ), may be able to be used in some engines  with little or no modification. Electricity can be used as a transportation fuel to power battery electric vehicles, fuel cell vehicles and in limited use in hybrid-electric vehicles.

Fuel cell vehicles use electricity produced from an electrochemical reaction that takes place when hydrogen and oxygen are combined in the fuel cell "stack. " The production of electricity using fuel cells takes place without combustion or pollution and leaves only two byproducts, heat and water. Even though the battery electric vehicle itself produces zero pollutants, when emissions from the power generating stations from traditional sources (coal, oil-fired or nuclear) are factored in, battery powered electric cars still produce less than 10 percent of the emissions of standard internal combustion engine cars.

Clean electricity production is possible in future years since the wind and solar power generating stations are becoming as a sources. Maintenance for battery electric vehicles is less, which have fewer moving parts to service and replace, although the batteries must be replaced every three to six years. Plug-in hybrid electric vehicles (HEVs) are hybrid cars with an added battery. As the term suggests, plug-in hybrids - which look and perform much like "regular" cars - can be plugged in to a 120-volt outlet (for instance each night at home, or during the workday at a parking garage) and charged.

Plug-ins run on the stored energy for much of a typical day's driving - depending on the size of the battery up to 60 miles per charge, far beyond the commute of an average American - and when the charge is used up, automatically keep running on the fuel in the fuel tank. A person who drives every day a distance shorter than the car's electric range would never have to dip into the fuel tank. Most of the energy used by plug-ins comes from electricity and not from gasoline.

That electricity can be generated efficiently and cleanly from America's abundant domestic energy resources, thus greatly reducing our dependence on imported oil. Unlike in the 1970s, when much of our electricity was generated from oil, today only 2% of our electricity is generated from oil. Hydrogen storage returns around 47% of original energy, while advanced batteries return 75-85%. According to the report, using electricity to charge electric vehicles (EVs) provides twice the miles per kilowatt hour than employing electricity to make hydrogen fuel.

Lithium ion batteries developed for portable electronics can store electricity at an energy density about six times greater than conventional lead acid batteries and in the future could go nearly 250 miles between charges. P-Series fuel is a mixture of natural gas liquids (pentanes plus), ethanol, and methyl tetrahydrofuran(MTHF), a biomass-derived co-solvent. P-Series is predominantly derived from renewable resources and burns much cleaner than gasoline. It can be mixed with gasoline in any proportion and is used in multi-fuel vehicles. Pure Energy Corporation holds the exclusive worldwide license to produce and supply P-Series fuel.


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Alternative Fuels for Automobiles. (2016, Jul 05). Retrieved from

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