If electricity prices are favorable, larger fractions of lignocellulosic material can be used as fuel for production of electricity in the integrated first and second generation ethanol production process. In this case, the cogeneration system must include condensing-extracting steam turbines to convert into electricity the amount of steam that exceeds the process requirement. Therefore, depending on the degree of flexibility in this process design, more or less lignocellulosic material will be diverted for electricity production (thus reducing the fraction of lignocellulose available for use as feedstock in second generation ethanol production) for optimizing economic returns.
In this work rigorous simulations of the integrated first and second generation bioethanol production were carried out using Aspen Plus, evaluating different configurations of the cogeneration system in order to assess the impact of its flexibility depending on the relative electricity and second generation ethanol prices. Environmental assessment (LCA) and a preliminary economic analysis were carried out to indicate which configurations lead to the best economic and environmental results, as a possible basis for decision-making. Sensitivity analyses were also carried out to show in which conditions cogeneration flexibility may be of benefit.