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The first four aliphatic alcohols (methanol, ethanol, propanol, and butanol) are of interest as fuels because they can be synthesized biologically, and they have characteristics which allow them to be used in current engines. One advantage shared by all four alcohols is octane rating. Butanol has the additional attraction that its energy per kilogram is closer to gasoline than the other alcohols (while still retaining over 25% higher octane rating). As Of 2005 , production of all four alcohols from petroleum is cheaper than fermentation and extraction from biomass, but this is expected to change as fermentation and extraction processes become more efficient while petroleum becomes more expensive. =Methanol and Ethanol= Ethanol and Methanol both have advantages and disadvantages over fossil fuels, such as petrol and diesel. For instance, ethanol can run at a much higher compression ratio without octane-boosting additives (its octane rating is 129 as opposed to 91 for plain petrol), and it's cleaner - because ethanol molecules contain oxygen, carbon monoxide emissions can be 80-90% lower than for fossil-fuelled engines. Also, ethanol's latent heat of vaporization is higher than petrol's - more heat energy is needed to vaporize it, so it cools an engine down better than petrol - ethanol's LHV is ~250% higher than that of petrol. Methanol shares more or less the same advantages. But there are disadvantages too. Ethanol is corrosive and has 37% less energy per litre than petrol. Methanol is even more corrosive and its energy per liter is 55% lower than that of petrol. High compression ratios and corrosion-resistant materials can overcome these issues, but require extensive engine modification. USE OF METHANOL Methanol has also been proposed as a fuel of the future. Extensive use of Methanol Fuel could spark the growth of a Methanol Economy . The main hazard of methanol is its toxicity. Methanol fuel is widely used in motorsports, especially in Drag Racing , Monster Trucks, and Mud Racing. Mark Thomas has used Ethanol on his IHRA Top Alcohol Funny Car for years. In 2007, the Indy Racing League will use ethanol exclusively in their cars. USE OF ETHANOL Ethanol is already being used extensively as a Fuel Additive , but the use of Ethanol Fuel alone or as part of a mix with gasoline is increasing. =Propanol and Butanol= 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, but a difficulty for starting engines, particularly in cold weather. In comparison, methanol, ethanol, and propanol have flashpoints of 11, 13, and 15 °C respectively. The fermentation processes to produce propanol and butanol from cellulose are fairly tricky to execute, and the Weizmann Organism (''Clostridium acetobutylicum'') used to perform these conversions produces an extremely unpleasant smell that must be considered when designing and locating a fermentation plant. This organism also dies when the butanol content of whatever it is fermenting hits 7%. For comparison, yeast dies when the ethanol content of its feedstock hits 14%. Specialized strains can tolerate even greater ethanol concentrations =Related Articles= |
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