Decision-makers should strive for an efficient employment of resources for the whole industrial ecological system. The metabolization of resources should be optimized in thermodynamic terms. This contribution presents an effort to use exergy analysis as a quantitative tool in the thermodynamic optimization of the life cycle of plastics. Quantitative results on overall exergetic efficiencies of different industrial metabolic options are presented. Therefore, different waste treatment options of plastics will be considered, taking into account interacting industrial activities, such as virgin plastics production and heat and electricity production starting from natural resources. Copyright (C) 2004 John Wiley Sons, Ltd.