Numerous sustainability assessment methods, especially environmental performance evaluation tools, have been developed to assess environmental performance of the process industry. Typically, environmental performance indicators cover only primary emissions and consumption without any recognition of secondary environmental burdens from auxiliary processes outside the plant boundaries. Therefore, the environmental impacts of the production site might be decreased whereas the overall environmental performance is not necessarily improved. The overall objective of our research project is to develop a sustainability index that comprehensively and reliably captures the environmental, economic, and social sustainability of an industrial plant. In this paper, we present this work on environmental and economic sustainability metrics for the metal production industry and two hypothetical process industry case studies on the application of the developed metrics. We develop both appropriate indicators and an example of anenvironmental and economic sustainability index that is also tested in two process industry case studies. Our assessment approach integrates indicators and life cycle assessment by expanding the scope of the typical environmental performance indicators. By this approach, the evaluation not only concentrates on the activities at the plant site, but also covers the emission sources that are indirectly connected to the actual production process. As a result, this approach provides comprehensive information for decision-makers on both the environmental impacts caused by plant operations and economic implications of alternative decisions. In addition, we present a discussion of according EU and Finnish legislation and their implications for both the management and assessment of plant level environmental and economic sustainability performance.