A multi-objective, multi-period model for optimizing the design and operating strategy of district energy systems is proposed by authors [1]. In the developed model the process and energy integration techniques 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 decentralized conversion technologies and distribution networks, the environmental impacts can be reduced down to 50-65% and the total annual costs down to 22-27%. In addition, 75% efficiency is obtained due to the integration of co-generation technologies, endogenous resources and the waste heat recovery. (C) 2015 Elsevier Ltd. All rights reserved.