Model-based analysis of the limits of recycling for its contribution to climate change mitigation

Philipp Schäfer,Mario Schmidt

doi:10.1007/s00550-021-00515-7

Abstract

The concept of Circular Economy (CE) and its main strategy recycling are seen as one of the most important measures to achieve sustainable development. Meanwhile, however, concerns are being raised in the scientific community about the conceptualization and orientation of CE. One major issue is that CE is in danger of becoming an end in itself, with the goal of completely closed material cycles. Its contribution to sustainable development is gradually fading into the background. To contribute to this ongoing discussion, we focus in our article on the recycling of metals as part of CE and its contribution to climate protection, as one of the main aspects of sustainable development. Based on life cycle assessment and substance flow modelling carried out in our previous works, we show that metal recycling in most cases requires much less energy and therefore results in much lower greenhouse gas (GHG) emissions than primary production. However, this is by no means without limitations. We show empirically that metal concentration is a significant factor that determines the energy required for recycling. If the metals are too diluted in the technosphere, as it is indeed the case for several metal applications, their recycling require much more energy than the alternative primary production, and thus intensifying rather than mitigating climate change.

Highlights

The Circular Economy (CE) concept and its main strategy recycling have gained momentum
To make a contribution to this ongoing discussion on CE we focus in this article on how metal recycling relates to climate change mitigation
Metals are of high relevance in this context as their production contributes with up to 10% significantly to annual global greenhouse gas (GHG) emissions (IRP 2019), which is due to the high energy demand of this sector with up to 7% of global (IEA 2019)

Summary

Introduction

In the literature, many scientists express their concerns about the inconsistencies in the conceptualization of CE as well as its contribution to sustainable development (Allwood 2014; Blomsma and Brennan 2017; Bocken et al 2017; Cullen 2017; Kirchherr et al 2017; Korhonen et al 2018b). It is known that these developments hinder recycling (Dahmus and Gutowski 2007; Johnson et al 2007) It is known, based on physical laws, that the concentration of a material in particular affects the energy requirements of its extraction (Moreau et al 2017). As long as the energy production system is mainly based on fossil fuels, and this is definitely the case for the following decades (IEA 2020), this situation will only slightly change. Based on data from life cycle assessment and substance flow models, we present how the energy requirements relate to increasing EOL-RR for copper as an example metal Using this data for a comparative analysis with the energy requirements for primary production of copper, we determine energetic optimized EOL-RRs for the scope of Germany and the year 2014. We integrate the results from the previous chapters in a more holistic perspective

Metal concentration and end-of-life recycling rates

Optimized end-of-life recycling rates

Integration in a holistic perspective

Findings

Discussion, outlook and conclusion