Modeling circularity as Functionality Over Use-Time to reflect on circularity indicator challenges and identify new indicators for the circular economy

Journal of Cleaner Production, vol. 379, pp. 134797

Abstract

The Circular Economy describes an economic system that creates value without causing unrecoverable waste, a growing problem of the Anthropocene. The question remains what solutions to reversing this course could look like and how indicators should be designed to measure their capabilities to constitute a circular economy. These indicators should allow for a nexus approach, i.e., consider synergies and trade-offs with other important social, environmental, and economic factors. Earlier research shows a research gap in indicators able to assess value change and retention, i.e., the preservation of specific functions instead of products in general. Aiming to fill this gap, in this article, we discuss using the concept of functionality from Life Cycle Assessment over the time product systems are used to measure circularity. We create a Functionality Over Use-Time (FOUT) graph and use it to illustrate the challenges of existing circularity indicators. The challenges are grouped into four clusters: 1) multi-cyclic longevity; 2) up- & downcycling effects; 3) measuring disruptive change instead of incremental change; 4) integration into sustainability assessment. We discuss how considering FOUT could solve these challenges and propose two novel indicators derived from the approach: A functional circularity indicator and a cross-functional circularity indicator. The functional circularity indicator measures the integral surface of functionality over the use-time of the original product's materials. The cross-functional circularity indicator measures the time a product's functionality is reduced by half. Finally, FOUT modeling and the indicators are exemplified in a comparative case study of a steel-reinforced concrete double wall and a Carbon Reinforced Concrete double wall. Further case studies are needed for future research, including FOUT indicator integration in Life Cycle Sustainability Assessment and a detailed representation of the 10R in FOUT modeling.

Authors 4

1. Tobias Hatzfeld corresponding

   Institute for Integrated Management of Material Fluxes and of Resources · United Nations University · Technische Universität Dresden

   Affiliation as printed

   Institute for Integrated Management of Material Fluxes and of Resources (UNU-FLORES), United Nations University, 01067, Dresden, Germany

   Sustainability Management and Environmental Accounting, Faculty of Business and Economics, Technische Universität Dresden, 01062, Dresden, Germany

2. Jana Gerta Backes Aachen Institute of Sustainability in Civil Engineering

   RWTH Aachen University

   Affiliation as printed

   Institute of Sustainability in Civil Engineering, RWTH Aachen University, Mies-van-der-Rohe Str. 2, 52074, Aachen, Germany

3. Edeltraud Guenther

   Institute for Integrated Management of Material Fluxes and of Resources · United Nations University · Technische Universität Dresden

   Affiliation as printed

   Institute for Integrated Management of Material Fluxes and of Resources (UNU-FLORES), United Nations University, 01067, Dresden, Germany

   Sustainability Management and Environmental Accounting, Faculty of Business and Economics, Technische Universität Dresden, 01062, Dresden, Germany

4. Marzia Traverso Aachen Institute of Sustainability in Civil Engineering

   RWTH Aachen University

   Affiliation as printed

   Institute of Sustainability in Civil Engineering, RWTH Aachen University, Mies-van-der-Rohe Str. 2, 52074, Aachen, Germany