1. Biological Process for Butanol Production
Chapter 3
Biological Process for Butanol Production

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

3. 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.

4. 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.

5. Feedstocks for Biobutanol Production
Starch
Molasses
Lignocellulose

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

7. 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.

8. 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.