-Environmental impact assessment is becoming indispensable for the design and operation of chemical plants. Structured and consistent methods for this purpose have experienced a rapid development. The more rigorous and sophisticated these methods become, the greater is the demand for convenient tools. On the other hand, despite the incredible advances in process simulators, some aspects have still not been sufficiently covered. To date, applications of these programs to quantify environmental impacts have been restricted to straightforward examples of steady-state processes. In this work, a life-cycle assessment implementation with the aim of process design will be described, with a brief discussion of a dynamic simulation for analysis of transient state operations, such as process start-up. A case study shows the importance of this analysis in making possible operation at a high performance level with reduced risks to the environment.