**1. Introduction**

What is the circular economy? This is a frequently asked question. Is it a model analysis tool, a process framework, or an innovative way of defining public policy? The Circular Economy is a set of strategies that requires evaluating and developing new business models to transform circular strategies into competitive advantages, business resilience, and successful revenue models, within the limits of planet Earth. Using fewer natural resources and pursuing near-to-zero waste targets.

It is clear that sustainable development cannot be regarded merely as an environmental statement to the extent that economic and social issues are closely related. A change of mentalities is needed, basically in what concerns the consumption patterns that are implied in what is still today understood as the quality of life, if sustainability is to be attained.

Sustainability is necessarily subjective because it reflects human value — the relative importance stakeholders assign to the activity to be sustained, to the perceived benefits of that activity, and to other values "traded-off" to sustain the activity in question [1]. Additionally, due to the fact that sustainability is a long-term issue and the effects of non-sustainable behavior are often delayed in time, companies tend to focus their effort on short-term issues and avoid problems that are not imminent.

However, many companies are becoming increasingly conscious of the need to change their practices.

In fact, the environmental strategies of companies have been evolving over time. The first strategies to be introduced were of a compliant nature, that is. strictly related to environmental regulation and pollution control, and were therefore process-oriented. In order to assess compliance, these strategies make use of tools such as energy and environmental audits. Improved strategies arise with extended environmental consciousness and product responsibility, introducing life-cycle thinking.

The focus of these strategies is on products/services and on the minimization of the environmental impact throughout their life cycle, that is. from the extraction of material to final product disposal, passing the use stage. Life cycle assessment (LCA) is an assessment tool for the environmental performance of the product or service that accounts for all the relevant flows of energy and materials [2].

Design for sustainability emerges in this strategic context as a life-cycle thinking design approach in which the design goals are those of minimizing the consumption of resources, minimizing emissions, and facilitating the disposal of the product at its end-of-life, ideally with good prospects for reuse and recycling. Life cycle assessment is the preferential tool for assisting the design of the sustainability process. Finally, it is necessary to mention that the most recent and holistic environmental strategies are those based on industrial ecology. These strategies are aimed at closing loops in industrial ecosystems, namely by promoting the exchange of waste across industrial sectors and energy cascading utilization and are therefore system-oriented.
