Energy and water targeting of ethanol production processes: A review

Global production of biofuels, e.g., ethanol, biogas, and biodiesel, has increased to 30 billion gallons per year, of which 75% is ethanol. Ethanol can be produced from sugar, starch, and lingocellulose-based raw materials. Based on the type of feedstock, the whole process and energy and water consumptions may significantly vary. High energy costs in European countries and lack of water resources in some Asian countries, especially in the Middle East, are the main concerns of process engineers. In this paper, the energy and water sinks as well as their sources were reviewed for different ethanol production processes. In most of these cases, the major parts of energy are used in dehydration, stillage evaporation, and distillation units. Ethanol distillation columns and condensation processes are wastewater, can be purified and recycled. Water is crucial in fermentors, dilution tanks, and cooling towers. A two-stage approach is suggested for the minimization of water and energy consumption. First, it is required to optimize the amount of energy by, for instance, using multiple pressure distillation columns and increasing fermentation temperature. Second, water consumption should be reduced, e.g., by the application of concentrated hydrolysis or solid state fermentation. It was proved that minimization of energy consumption and water demands have direct effect on each other. Furthermore, it was possible to reduce 50% of water and energy consumption in sugar and starch-based ethanol production. Finally, the application of each strategy depends on the cost and availability of energy and water.

کلیدواژه ها:

Energy targeting ، Water targeting ، ethanol