Traditionally, comprehensive process design has relied on a sound and insightful techno-economic analysis framework. In particular, once a base-case design is selected, further analysis is carried out to assess the environmental impact as well as possible process safety implications. Furthermore, limited modifications to the base-case design are typically carried out to concurrently address environmental and safety concerns. This sequential approach can thus lead to suboptimal process system designs when multiple objectives of profitability, sustainability, and safety are considered. Indeed, the simultaneous consideration of these objectives during the conceptual design phase of a project should lead to superior performance profiles. In the present work, a new approach for the incorporation of safety and sustainability considerations early enough during the conceptual design of the process is presented. This approach is based on extending the conventional return on investment (ROI) analysis to include positive or negative impacts of potential design changes that emerge when sustainability and safety issues are simultaneously considered. Within the proposed context, this becomes possible through a meaningful and potentially insightful extension of the traditional economic performance metric to account for safety and sustainability-relevant performance criteria. In particular, a safety and sustainability weighted return on investment metric (SASWROIM) is introduced to systematically integrate the aforementioned multiple objectives and therefore inform the conceptual design stage in a methodologically sound and insightful manner. To illustrate the usefulness of the proposed approach, two case studies on the production of butadiene and methanol are considered and analyzed within the above context. It is demonstrated that this new approach can be used by decision makers to reliably evaluate the economic viability of a project as well as the assorted impact on the environment and process safety.

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