Butanol is a higher energy alcohol than ethanol (105 kBtu vs 70 kBtu per gallon), making it an attractive alternative to ethanol. Because of this, it does not require engine modification like ethanol, which gives it an advantage, however it is more difficult to make, requiring higher levels of distillation energy because the max concentration is 2.5% vs 14% for ethanol.

Butanol can be made from all the same feed stocks as ethanol, but it is not made with yeast, rather 2 different bacteria. One bacteria turns the sugar and starches into butyric acid, and then another takes over and turns this into butanol. This process is historically referred to the ABE process, as Acetone, butanol, and Ethanol are produced simultaneously, however 2-3 times more butanol is produced than Acetone.

The trouble with butanol has always been in the purification process. Because concentrations above 2.5% start to kill the butanol making bacteria, several methods are being explored for increasing output. One is genetically modification of the bacteria, but for our DIY fans, absorption or molecular sieves seem to be the best bets. There are several hydrophobic membranes out there that will allow butanol to pass, but will prevent the water form going through. This is like a water filter and allows for a continuous flow production. Absorbing the butanol into an oil or solid material could also prove to be very efficient. As of 2008, no open-source butanol projects employing these methods have been published. Hopefully, someone out there will make this happen.

Using butanol is super easy. Put it in your car and go! Folks have made cross-country journeys on butanol and have proved that lower emissions and one-to-one replace for gasoline is completely viable. If we can get the production side of butanol figured out, it could become the next wonder-fuel.

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