This editorial and overview of a Special Issue dedicated to the 11th Conference Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction - PRES 2008. Thirteen papers have been selected and after being peer-reviewed. Nine were accepted for publication covering important subjects of energy generation and usage. They are focusing on recent development of various features of heat integration which is an important methodology for increasing energy efficiency and saving. The complementary issues covered are emissions reduction and the security of energy supply. This issue of ENERGY is the fourth special journal issue dedicated to selected papers from PRES conferences. (C) 2009 Elsevier Ltd. All rights reserved.