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Butanol is an alcohol that can be used as a transport fuel. It is a higher member of the series of straight chain alcohols with each molecule of butanol containing four carbon atoms rather than two as in ethanol.

Biobutanol can be produced by fermentation of biomass by the A.B.E. process. The process uses the bacterium Clostridium acetobutylicum, also known as the Weizmann organism, or Clostridium beijerinckii. It was Chaim Weizmann who first used C. acetobutylicum for the production of acetone from starch (with the main use of acetone being the making of Cordite) in 1916. The butanol was a by-product of fermentation (twice as much butanol was produced). The process also creates a recoverable amount of H2 and a number of other by-products: acetic, lactic and propionic acids, isopropanol and ethanol. A problem is the relatively low-yield and sluggish fermentation, as well as problems caused by end product inhibition and phage infections.

Biobutanol can also be made using Ralstonia eutropha H16. This process requires the use of an electro-bioreactor and the input of carbon dioxide and electricity.

85% Butanol/gasoline blends can be used in unmodified petrol engines. It can be transported in existing gasoline pipelines and produces more power per litre than ethanol. Biobutanol can be produced from cereal crops, sugar cane and sugar beet, etc, but can also be produced from cellulosic raw materials. The difference from ethanol production is primarily in the fermentation of the feedstock and minor changes in distillation. The feedstocks are the same as for ethanol

There is no commercial scale production of biobutanol and a DEMO plant announced to start construction 2016 by the South Korean refiner GS Caltex is apparently not realized.