Biobutanol
Published by Butanol can be used in car engines as a replacement for conventional petrol (gasoline).
It is more similar to the compounds which already exist in petrol than ethanol is because of the longer hydrocarbon chain attached to the hydroxyl group. It has been shown that butanol can be used in car engines without the need to modify them. Butanol is called biobutanol when it originates from the biological processes of living organisms.
Butanol is one of the products of the ABE Process which involves the fermentation of biomass, in a similar way to making alcohol via the fermentation of fruits. A specific type of bacterium is required for the process. Its scientific name is Clostridium acetobutylicum, but it is sometimes called the Weizmann Organism. The process was developed in 1916 by Chaim Weizmann who intended to use starch to synthesise acetone, which was needed to make Cordite. It was found that butanol was also made by the process, in fact double the amount of acetone. Amongst other things, isopropanol, ethanol and carboxylic acids are also created in varying quantities.
Minor modifications from ethanol fermentation are required for butanol fermentation such as the was the biomass is used and variations in distillation since the products will have varying properties. Otherwise, it is possible to use the same plant matter for either butanol or ethanol production. Wheat or sugar crops are ideal starting materials and it has been suggested that less-useful plant matter like straw and grass clippings could also be put to use in this way.
BP and Du Pont have joined forces with the intention make biofuels a commercial reality. A research company in Switzerland, called Butalco, is trying to make biobutanol from yeasts which have been genetically modified for this purpose. They intend to use cellulose as the starting material. There are about a dozen such companies with the intention to make biobutanol the next big thing in alternative energies.
Butanol causes less damage than ethanol does through corrosion and less contamination of water, therefore less damage to petrol pipe lines. Butanol is also far more miscible with either petrol or diesel than ethanol. Tests are on-going into the efficacy of biobutanol in unmodified internal combustion engines. It is reckoned that about one-tenth more butanol is required to go a set distance relative to petrol, although the full effects of fuel economy are currently unclear.
Biobutanol has an octane number between 78 and 89, depending on the isomer produced by the fermentation. The more heavily branched t-butanol has the nigher octane number and can be added to petrol but cannot be used on its own because it is still a solid in temperatures up to 25°C, which would make it unusable anytime except a warm summer’s day. The octane number is an important consideration however, since a low octane number causes reduced engine performance and damage to the engine itself.
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