Lee Enterprises Consulting, Inc.

Lee Enterprises Consulting, Inc.


Butanol is a four carbon straight chain primary alcohol which has gained enormous attention as a potential gasoline substitute in recent years. This is due to its high energy density, low vapor pressure, low heat of vaporization and high hydrophobicity. These promising physical and chemical properties of butanol make it suitable for blending with or direct substitution of gasoline. Biobutanol can be produced through a fermentation process, using Clostridium acetobutylicum, which naturally produces acetone, butanol and ethanol in a 3:6:1 ratio. Historically, however, it was produced from starch and was outcompeted by petroleum-based butanol production.

Biobutanol can occupy a significant portion of the advanced biofuel markets in the future, if economics of the fermentation process improve. As a fuel, butanol has describable characteristics not shared by ethanol or fatty acid methyl ester biodiesel. Its low vapor pressure and hydrophobicity (which minimizes water retention) allows its use in established gasoline infrastructure. Also, compared to ethanol, it has 30% more energy, and is less flammable. It can be used in unmodified internal combustion engines blended with gasoline at any concentration (as opposed to 10%-15% for ethanol). Its low vapor pressure facilitates its application in existing gasoline supply channels, and it is less hydrophilic, less volatile, less hazardous to handle, and less flammable than ethanol. The ability to convert both hexose and pentose sugars provides a significant advantage over ethanol-producing yeast which can only consume hexose sugar. This allows the use of a much wider variety of feedstocks, including low cost waste materials.

Butanol’s toxicity, low yield, and high recovery costs are the main challenges of production by fermentation. Thus, despite its superior fuel properties, biobutanol does not yet enjoy the economies of scale of corn starch-based bioethanol production as it continues to be developed in a cost-per-unit-of-energy-produced manner.

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