Integrating Sustainability into Model-Based Systems Engineering: A Lifecycle-Oriented Methodology for Circular Industrial Product Design

Sustainable transition of industrial products requires moving beyond late-stage environmental assessment towards early, system-level decision making. Model-Based Systems Engineering (MBSE) provides a structured framework to embed sustainability requirements within product development, but its current application often remains focused on functional, technical and cost-related aspects. This paper proposes an integrated sustainable MBSE methodology in which the environment is treated as a primary stakeholder, together with users, manufacturers, maintainers, regulatory bodies and affected communities. Qualitative eco-design tools, such as the LIDS Wheel and eco-checklists, are used to elicit sustainability-driven requirements, while a proxy-based Life Cycle Assessment (LCA) supports the quantitative comparison of alternative circular strategies already at concept design stage. To better align with the design of socio-technical systems, the approach is extended toward Life Cycle Sustainability Assessment (LCSA), including not only environmental performance but also economic feasibility, social impact, maintainability, usability and emotional durability as drivers of product life extension. The proposed workflow links sustainability requirements to system architecture, functional decomposition and lifecycle scenarios, allowing designers to compare competing strategies such as reuse, repair, remanufacturing, refurbishing and recycling before detailed design synthesis. The methodology is demonstrated through multiple test cases with different levels of system complexity. Solar panels and internal combustion engines are used to discuss circular end-of-life strategies and proxy-based LCA at system level. A wind-turbine gearbox is then introduced as a mechanical engineering case study, where a parametric LCA model is developed by decomposing the system into assembly, sub-assemblies and components, enabling the comparison of materials, manufacturing processes, transport and end-of-life scenarios. The results show how sustainability-oriented MBSE can support early trade-off analysis, guide circular design decisions and promote a more human-centered and lifecycle-aware development of complex industrial products.