The circular economy has become an important issue in recent years because it makes sustainable development feasible by creating value in the economy and by closing the energy and materials loops. However, since most companies continue to operate under a linear model, it is particularly important to start providing companies with tools that facilitate their shift to the circular paradigm. The main objective of this research is to establish the key elements that are necessary for assessing the level of circular economy implementation. To that end, the Delphi method is used to validate and define the key elements of three categories: circular economy fields of action, industrial symbiosis, and environmental certifications. As a result, this study identifies the key elements that assess the degree of circular economy implementation and that allows small and medium‐sized enterprises to understand where they are and what they need to do to improve their performance.

Purpose: This research analyzes the maturity of environmental management as well as the degree of to which the Circular Economy has been implemented in Basque SMEs.Design/methodology/approach: A total of 17 case studies were carried out in industrial SMEs companies in the Basque Country.Findings: The main results show that companies are limited to complying with the law and in many cases are worried about the image of the company, although they are not committed to environmental issues. There is still a lot to do in SMEs, as they are the companies that face the biggest challenges due to a lack of resources.Originality/value: Circular Economy aims to change a linear economy into promoting sustainability of the economy while also engaging in sustainable environmental protection. This research has focused on small and medium enterprises as they represent a 99% of companies in Europe and they are the ones that have the most difficulty reaching a stage of environmental excellence due to their limited resources.