A multi-objective, multi-period model for optimizing the design and operating strategy of district energy systems is proposed by authors . In the developed model the process and energy integration tech- niques are principally investigated. In the present work, a case study is discussed to demonstrate the proposed model. The results illustrate that by selecting the adequate resources, centralized and decen- tralized conversion technologies and distribution networks, the environmental impacts can be reduced down to 50e65% and the total annual costs down to 22e27%. In addition, 75% efficiency is obtained due to the integration of co-generation technologies, endogenous resources and the waste heat recovery.