The integration of environmental impacts in the conceptual process design procedure can be achieved by combining Life Cycle Assessment (LCA) tools with flowsheeting software and process integration techniques. However, current LCI databases assume a given unit process chain for each product or waste, and do not allow for the systematic synthesis of the process chain minimizing the environmental impacts of raw materials or auxiliary flows, accounting systematically for the different alternatives and recyclings. This paper presents a methodology for systematically designing process units LCI database for the optimal design of integrated systems with a life cycle perspective.