Greater circularity leads to lower criticality, and other links between criticality and the circular economy

The modern world is reliant on metals, so a secure and stable supply is vital.

Tercero, Luis & Schrijvers, Dieuwertje & Chen, Weiqiang & Dewulf, Jo & Eggert, Roderick & Goddin, James & Habib, Komal & Hagelüken, Christian & Hurd, Alan & Kleijn, René & Ku, Anthony & Lee, Min-Ha & Nansai, Keisuke & Nuss, Philip & Peck, David & Petavratzi, Evi & Sonnemann, Guido & Voet, Ester & Wäger, Patrick & Hool, Alessandra. (2020). Greater circularity leads to lower criticality, and other links between criticality and the circular economy. Resources, Conservation and Recycling. 159. 104718. 


The modern world is reliant on metals, so a secure and stable supply is vital.

Security of supply is often assessed by considering the vulnerability of certain countries, sectors or companies (for example) to supply restrictions of a given raw mineral.

At the same time circularity considers how we can use the materials we already have for longer, reduce waste, increase efficiency, and create a circular economy for recyclable materials.

However, with a few exceptions, minerals are often not a part of this debate. Historically, policymakers have given most consideration to the circularity of the most obvious or commonplace materials, such as iron and paper, with less focus on rarer metals and minerals.

Such materials, like gallium, selenium, neodymium and dysprosium have important applications in wind and solar renewable power technology.

Assessing criticality can help us to prioritise the minerals for which we need to achieve better circularity.

This in turn will help the world to avoid the real risks of short, or no, supply.

Diversity and stability of primary supply are fundamental to assessing criticality. Many models for circularity have security of supply as an objective, but notably tend not to consider how to achieve that security.

Recycling is a key consideration in assessing criticality because it can benefit supply independence and complement supply above just the amount of virgin raw material we can extract.

Some critical materials can even be produced as a by-product of other mined metals, therefore being interdependent on the supply of the host metals.



  • Scientific circularity and criticality assessments don’t always consider the economic viability of recycling a certain material. But in reality, economic viability is another critical consideration for governments and industry
  • The quality and quantity of the end-of-life material to be recycled cannot be guaranteed
  • Appropriate facilities can be hard to find, and some metals that we would ideally like to also recycle can be lost in the necessary chemical or thermal separation processes which need to take place to recycle the primary material
  • International leaders should establish a framework setting out indicators and targets for the circularity of critical materials



When considering circularity, the shorter loops (such as repair, reuse, recycling of scrap or by-product) can often be overlooked.

But they could be critical in limiting the expected growth in demand for metals, including critical metals.

To further highlight the complex interdependency of these matters, the processes to close these short loops can often be themselves reliant on the use of critical metals.

To combat the inherent complexity, attention must be given at the highest levels of politics and industry to selecting materials which are compatible with recycling technologies in the first place and make it easy to do so – a point made by the UN International Resources Panel in 2013.

Moves towards modularity will also help in these efforts. An example of this in terms of a consumer product is the FairPhone, a mobile phone designed to have all of its parts be individually removed, replaced by the user, and ultimately recycled.

The concept is to give the item longevity – so that when parts of the technology inevitably break or fail, they can be easily swapped out and repaired. This is in contrast to the most popular phones we see these days, where individual parts are not repairable or removable by the individual consumer and therefore often when one part of the technology breaks, the whole item is discarded.

Mass economic viability of this kind of model is, however, another matter currently.

But designing for circularity at scale globally would mean increased recyclability and product longevity, therefore supporting security of supply.



Being flexible in our application of metals and minerals will also be key, such as through “substitution,” which means delivering the same function through different raw materials – ideally, ones with the most secure, sustainable supply and good recyclability.

This has relevance when considering both criticality and circularity.

Criticality assessments consider replacing (or substituting) the most critical metals with technology or materials more readily available.

Circularity assessments consider the impact of such substitute materials on the inflow of nonrecoverable and non-biodegradable materials to the process.

Mitigating criticality – scarcity or vulnerability of supply – can therefore be achieved by achieving and fine tuning the processes and outcomes of circularity, or a circular economy.

In terms of recycling, the considerations of both circularity and criticality are aligned. Closing those shorter loops is perhaps less simple, long term planning, logistical considerations needing to be considered, and the possibility that trade-offs might need to be made.



This paper rightly concludes that it is key to keep adapting and learning. Only this way will we build the societal basis and technological infrastructure needed to ensure a reliable, secure and long-term supply of the raw materials and minerals we need for our future.