A fuzzy multiple-objective approach to the optimization of bioenergy system footprints

Current interest in the large-scale use of biofuels has grown in response to both energy security and climate change concerns; however, it is also increasingly apparent that these benefits can come only at the expense of increased demand for agricultural resources such as land and water. Furthermore, recent studies also suggest that changes in land use patterns for energy crop cultivation can incur significant carbon debts that can only be recovered after many years of operation. The environmental feasibility of the use of energy crops to make biofuels can thus be viewed in terms of three main performance indicators-the land use, water and carbon footprints arising from a given level of system output. An optimal solution thus needs to account for tradeoffs that may be inherent in the conflicting objectives. This work presents a fuzzy multiple-objective modeling approach for determining optimal bioenergy system configuration given targets for the three footprint metrics. The fuzzy optimization approach is integrated with an input-output-based life cycle model for establishing system material and energy balances. The approach is demonstrated here through the analysis of different scenarios for the integrated production of biodiesel, ethanol and electricity under anticipated energy demand conditions in the Philippines. (C) 2009 Published by Elsevier B.V. on behalf of The Institution of Chemical Engineers.