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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.
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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 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.