(41c) LCA-Based MINLP Synthesis of a Bioethanol Production Network

This paper presents an integrated, sustainable, mixed-integer nonlinear programming (MINLP) synthesis of bioethanol production processes from different raw materials, which include starchy crops and lignocelluloses. The entire production network also comprises the agricultural supply and transport sectors. Life Cycle Analysis is performed simultaneously with the synthesis. A special normalized LCA index is defined and included in the multi-criteria optimization for determining several environmental impacts from ?cradle? to ?grave?, where the economic criterion is defined as a profit, social criterion as a conversion of food-intended raw materials into energy, and environmental criterion as different environmental burdens. A two-level MINLP approach is performed where a relatively simple and yet economically-effective production of bioethanol from corn is considered at the first level. At the second level, the superstructure is expanded with sustainable alternatives using other raw materials and the objective function augmented for the LCA environmental criteria in order to generate a set of Pareto optimal solutions. An overall multi-technology process network scheme in contrast to single-technology schemes enables the simultaneous conversion of different raw materials into ethanol, consumes smaller amounts of utilities, and requires smaller investment. The syntheses are performed by employing an MINLP process synthesizer MIPSYN.