Overview of Continuous Alcohol Fermentation and Multipressure Distillation Technology

Ethanol production from agro-based raw materials normally involves two major steps, fermentation and distillation. These steps are reviewed, mainly in relation to molasses, which is the most common raw material in tropical countries. The specific effect on fermentation efficiency of molasses quality in terms Fermentable Sugars, the ratio of fermentable to non-fermentable solids, Volatile Acids, Caramel and other inhibitors and Calcium and other inorganic elements are discussed. The improvement in fermentation kinetics by using efficient yeast strains and hygienic yeast propagation with cell recycle is also discussed. Major aspects of ethanol fermentation by various techniques are discussed. The advantages and limitations of batch fermentation, its variants, and those of continuous fermentation, based on operational experiences from commercial scale ethanol plants are discussed. The concept of Pressure cascading distillation (multi pressure distillation) and its advantages over atmospheric distillation is described. It is concluded that an efficient fermentation plant coupled with multi pressure distillation system can provide competitive advantage for ethanol producers.