Biological Process for Butanol Production Chapter 3 Biological Process for Butanol Production

Butanol An aliphatic saturated alcohol An industrial commodity Currently produced from petrochemicals Used as a solvent

Comparison of Fuel Characteristics of Gasoline and Bioalcohols Energy Density Air-Fuel Ratio Heat of Vaporization Research Octane Test Motor Octane Test Gasoline 32 MJ/L 14.6 0.36 MJ/kg 91-99 81-89 Butanol 29.2 MJ/L 11.2 0.43 MJ/kg 96 78 Ethanol 19.6 MJ/L 9.0 0.92 MJ/kg 130 Methanol 16.0 MJ/L 6.5 1.20 MJ/kg 136 104 Ref: Cheng, J. (2010) Biomass to Renewable Energy Processes Butanol appears superior to ethanol due to its similarity of its fuel characteristics with gasoline, non-corrosive nature, and unrestricted miscibility with conventional fossil fuel.

Advantages of Biobutanol It contains 25% more energy (Btus) than ethanol, since it has four carbons versus two in EtOH. It can be produced biologically from the materials such as corn, grasses, leaves and agricultural residues. It is safer to handle due to its lower evaporation when compared to gasoline and ethanol. It can be used in the existing engines in pure form or blended in any ratio with gasoline, while ethanol can be blended up to 85% only. It can be transported through the existing pipelines due to its low corrosive properties. It is a green fuel without SOx, NOx, or carbon monoxide (CO) emissions when burned in internal combustion engines.

Feedstocks for Biobutanol Production Starch Molasses Lignocellulose

Microbial Cultures Starch/Celluloses Glucose, pentose Lactic acid Acetic acid Ethanol Acidogenesis Acetone Solventogenesis Butyric acid Butanol Clostridium acetobutylicum

ABE fermentation ABE (acetone-butanol-ethanol) Divided into 2 stages: Acidogenesis Solventogenesis For C. acetobutylicum, solvent production at pH 5.5 or lower (optimum at 4.3) Process modes: batch, fed-batch, continuous. Sometimes a combination of processes are used.

Biobutanol Recovery In the fermentation broth, butanol is often less than 20 g/L. Apart from the traditional distillation technology, alternatives for downstream separation and purification technologies include membrane-based systems (RO, pervaporation, perstraction and membrane evaporation), in-situ gas stripping and liquid-liquid extraction.