  Implementing circular economy (CE) principles is increasingly recommended as
a convenient solution to meet the goals of sustainable development. New tools
are required to support practitioners, decision-makers and policy-makers
towards more CE practices, as well as to monitor the effects of CE adoption.
Worldwide, academics, industrialists and politicians all agree on the need to
use CE-related measuring instruments to manage this transition at different
systemic levels. In this context, a wide range of circularity indicators
(C-indicators) has been developed in recent years. Yet, as there is not one
single definition of the CE concept, it is of the utmost importance to know
what the available indicators measure in order to use them properly. Indeed,
through a systematic literature review-considering both academic and grey
literature-55 sets of C-indicators, developed by scholars, consulting companies
and governmental agencies, have been identified, encompassing different
purposes, scopes, and potential usages. Inspired by existing taxonomies of
eco-design tools and sustainability indicators, and in line with the CE
characteristics, a classification of indicators aiming to assess, improve,
monitor and communicate on the CE performance is proposed and discussed. In the
developed taxonomy including 10 categories, C-indicators are differentiated
regarding criteria such as the levels of CE implementation (e.g. micro, meso,
macro), the CE loops (maintain, reuse, remanufacture, recycle), the performance
(intrinsic, impacts), the perspective of circularity (actual, potential) they
are taking into account, or their degree of transversality (generic,
sector-specific). In addition, the database inventorying the 55 sets of
C-indicators is linked to an Excel-based query tool to facilitate the selection
of appropriate indicators according to the specific user's needs and
requirements. This study enriches the literature by giving a first need-driven
taxonomy of C-indicators, which is experienced on several use cases. It
provides a synthesis and clarification to the emerging and must-needed research
theme of C-indicators, and sheds some light on remaining key challenges like
their effective uptake by industry. Eventually, limitations, improvement areas,
as well as implications of the proposed taxonomy are intently addressed to
guide future research on C-indicators and CE implementation.
