In the last decade, international organizations have expressed their concern about the capacity of classical economical indicators to encompass the whole story of the developing processes, especially in their relationship with the environment. A comprehensive environmental metrics has been adopted (states and organizations reports indicators like greenhouse gas emissions, ozone concentrations, surface of contaminated land, number of threatened species, etc.) and operates in parallel with the traditional industrial indicators. But it seems not enough since this complementary metrics does not illustrate the entire complexity of development processes, in the 21st Century. Recent EU documents stress the importance of sustainable development, of the importance of industrial symbiosis as a tool to better manage material, energy and human resources and evaluate the possibility of generating and reporting new, synthetic, composite indicators that could include both the information in the classical economical indicators but also the environmental impact and the quality of life. The paper is a contribution in this respect and, starting from the results of the implementation of the Industrial Symbiosis paradigm in the case of a power plant, it presents how the EU recommendations about a more sophisticated metrics of ecoefficiency works, for the first time at the level of a Romanian enterprise. An original, new metrics is generated, that takes into account whether and how the technological and economical processes are accompanied by a favourable trend for the environment, A new, composite index for ecoefficiency and sustainability is presented in its structure and dynamic evolution, enabling local managers not only to assess their sustainable development trend, but also to identify where should their action be directed in the short term to correct unfavourable trends. The study was a part of the PAZEWAIA Project financed by Innovation Norway.