Energetic and Environmental Assessment of Biomass to Ethanol Processing in the Sugar-Cane Industry

Bio-fuels have come to be recognized as possible, environmentally friendly alternatives to fossil fuels. This work studies a Bio-ethanol production process complementing a sugar mill, through computer simulations, using ASPEN PLUS® as the simulation engine.

The process flowsheet examined includes three major processing stages typical of distillery installations for fuel-grade production in typical sugar-cane processing facilities: (1) the fermentation stage, (2) the separation stage, and (3) the dehydration stage.

Using plant data from a bio-ethanol pilot plant in Northwestern Argentina (NOA) a kinetic model is formulated for a fed-batch molasses fermentation process. The model for this unit, along with a user-defined separation module, is then integrated into a commercial process simulator.  Different schemes meeting equivalent performance standards in terms of purity and recovery are examined in this paper.

Particular attention is given to energetic integration by performing a pinch-analysis to each of the fundamental stages to find a global optimum. Optimization is achieved by minimizing a given objective function that accounts for bio-ethanol recovery, separation efficiency, and minimization of effluents. Life Cycle Analysis is used to complete the assessment of operating parameters/conditions on environmental effects.