A framework for assessing and enhancing product circularity by translating circular design criteria into measurable requirements

The transition towards a circular economy (CE) is increasingly influencing engineering practices and product development. However, the concept of circular product design remains difficult to grasp, with existing circular design criteria lacking specificity and measurability. This paper proposes a comprehensive framework to translate these vague criteria into measurable requirements for product development to assess and improve a product's suitability for a CE. The presented methodology involves a three-step approach: collecting and analyzing standards-derived requirements, assessing a product's suitability for various R-Strategies based on the requirements, and identifying improvement opportunities via action portfolios. An industrial use case involving a centrifuge for liquid separation and discussion of results within an industry consortium through a SWOT analysis validated the applicability of the framework. Within this research, a structured list of measurable requirements for a circular product design was derived from circular design criteria from standards in the field of CE. Based on this list of requirements, an assessment of a product's suitability for the four circular strategies reuse, repair, remanufacture and recycle was examined with repair showing the highest suitability. An action portfolio was developed from the assessment results, outlining possibilities for action to improve product design at identified weak spots. However, the practical implementation of these improvements and reassessment of the product are beyond the scope of this study. The developed framework has been reported to be comprehensive and easy-to-implement. The integration of a scale-based assessment approach achieved measurability of the requirements and ease of application. The transparent assessment process allowed product developers to trace the impact of individual requirement changes and to adjust the overall assessment by weighting requirements against each other. Although some subjectivity remained due to the scale-based assessment approach, documented guiding questions helped ensure consistency across various iterations of assessment. While further quantification could enhance precision, this research contributes to advancing the transition to a CE in industrial practice by better aligning product design with CE standards and principles.