Biobutanol Basics

Biobutanol is a type of biofuel produced from biomass via fermentation. The potential feedstock for producing biobutanol is extremely varied, and includes all the common crops as well as agricultural wastes. Biobutanol is more similar to gasoline than ethanol, and thus has several advantages over ethanol as a biofuel.

Advantages of Biobutanol

There are many advantages to biobutanol over its competitor, ethanol.

• Unlike ethanol, biobutanol can be transported through a petroleum pipeline system and sellable through existing station pumps. This means its distribution and sales will be much less expensive than ethanol. This is due to the fact that biobutanol is much less polar than ethanol.
• Biobutanol has a higher energy density than ethanol. This would translate into more kilometers per liter than ethanol.
• Ordinary vehicles should be able to run without modifications on a higher concentration of biobutanol in gasoline than ethanol. The potential maximum could be as high as 16% biobutanol to gasoline.
• It will be possible to make biobutanol from both grain or cellulose.
• Biobutanol is an oxygenate, which means it increases the level of oxygen in gasoline and thus improves combustion.
• Biobutanol does not readily adsorb moisture (it is not hygroscopic), so is less affected by changes in the weather, unlike the combustion of pure ethanol, which requires engine and fuel system modifications.
• Biobutanol does not attack materials commonly used in vehicular internal combustion engines.

Production

The bacterium Clostridium acetobutylicum is commonly used to produce biobutanol.

The rod-shape, gram-positive bacteria Clostridium tyrobutyricum is first used to produce butyric acid and hydrogen using anerobic fermentation from glucose and xylose. The products are then passed along to another bioreactor containing Clostridium acetobutylicum, which converts the butyric acid into butanol. It is notable that C. acetobutylicum and many other Clostridia can digest whey, sugar, starch, lignin, cellulose fiber, and other biomass directly into butanol, propionic acid, ether, and glycerin.

There are however, some problems using this organism. It grows slowly, it's very fastidious, and it's not easy to genetically manipulate. Because of this, some researchers have engineered the common bacterium Escherichia coli to produce biobutanol, which makes it more feasible to produce it in industrial quantities. The researchers inserted two different nonnative genes into E. coli. The first gene came from a microbe commonly used in the production of cheese. The gene codes for an enzyme that converts keto acids into aldehydes. The second gene, derived from yeast, codes for an enzyme that converts aldehydes into butanol.

References:

Carson I and Vaitheeswaran VV (2007). Zoom: The Global Race to Fuel the Car of the Future. Twelve. 336 pages.

Paul B (2007). Future Energy. John Wiley & Sons, Inc. 226 pages.

Pernick R and Wilder C (2007). clean tech revolution. Collins. 308 pages.

Wikipedia Biobutanol.