1 Rödel, J. “On sustainability … A grain of humility,” ACerS Bulletin 2022, 101(7): 3.

2Circular economy action plan,” European Commission, March 2020. Accessed 13 July 2023.

3 Klöpffer, W. and Grahl, B., 2014. Life cycle assessment (LCA): a guide to best practice. John Wiley & Sons.

4 Klemenz, S., Stegmüller, A., Yoon, S., Felser, C., Tüysüz, H., and Weidenkaff, A. “Holistic view on materials development: Water electrolysis as a case study,” Angewandte Chemie International Edition 2021, 60(37): 20094–20100.

5 Johanning, M., Widenmeyer, M., Cano, G.E., et al. “Recycling process development with integrated life cycle assessment: A case study on oxygen transport membrane material,” Green Chemistry 2023, 25: 4735–4749.

6 Zampori, L, and Pant, R. “Suggestions for updating the Product Environmental Footprint (PEF) method,” Joint Research Center of the European Union, 2019. Accessed 13 July 2023.


letter to the editor

Evidence-based sustainable development and circularity of materials

To the editor:

In a recent letter,1 TU Darmstadt professor Jürgen Rödel stated, “Scientists need to move society onto a straight—but rocky and long—path to sustainability.” We firmly resonate with his view.

Materials scientists design materials based on the requirements of the intended application. These materials may contribute to a more sustainable world—for example, when used to create clean energy technologies, such as fuel cells—but how often do we acknowledge, evaluate, and rationalize the environmental impacts (EIs) linked to producing a material? In the instances when it is addressed, it is often considered at a late developmental stage where, due to economic reasons, a process modification is unfeasible, regardless of the EI results.

Transitioning to a sustainable circular economy will inevitably require us to pay more attention to recycling. For example, the European Commission’s Circular Economy Action Plan calls for products to be reusable, easier to recycle, and incorporate as much recycled materials as possible without affecting performance.2

However, recycling may not always be the most sustainable pathway to minimizing EIs because recycling is not entirely impact free. Consequently, the sustainability assessment of a specific recycling process needs to be quantifiably demonstrated.

Unfortunately, many reported recycling processes lack scientifically verified sustainability claims. Thus, without solid substantiation, these approaches are simply environmental marketing rather than enacting true sustainable change.

For these reasons, we strongly recommend integrating well-established scientific methods for environmental assessment, such as life cycle assessments (LCAs),3 into early-stage material processes and recycling developments to favor evidence-driven sustainability. Doing so will have the following concrete benefits.

  • Significant contributors or “hotspots” to the EIs of a material’s process and recycling can be identified and addressed at a relatively early stage.
  • Quantified environmental assessment data for the primary development of a material will be available and will allow for a direct comparison with the EIs of simultaneously developed recycling routes.

Our research group and collaborators have already started coupling LCAs with the development of new materials and recycling routes.4–5 In a recent work,5 we identified EI hotspots during the primary synthesis of a recently proposed and promising ceramic oxygen transport membrane material. To tackle one of the hotspots, a new recycling route was developed. Another LCA was performed on this recycling route, which allowed us to scientifically claim that the developed recycling route not only tackled the hotspot but reduced the EI in twelve out of fourteen categories.

However, as mentioned, recycling is not entirely impact free. Compared to the primary process, our recycling process consumes more energy and releases more process emissions. We are working to modify our methodology to resolve the remaining hotspots and report a process with the highest environmental performance.

Just as we cannot report functional advances in materials without supporting data, sustainability claims should only be made based on hard facts and unambiguous evidence. Our recommendation to perform a sustainability assessment during the early stages of materials/product development will help alleviate burden shifting and the need for difficult process modifications during later developmental stages. Additionally, higher technology readiness levels may be concomitant with complex resource flows—the Circular Footprint Formula offers valuable guidance in this area.6

By adopting these recommendations, we can move one step closer to attaining true sustainable development and recycling of materials.

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Rishabh Kundu,a Marc Widenmeyer,a Vanessa Zeller,b Emanuel Ionescu,a, c and Anke Weidenkaffa,c

a Technical University of Darmstadt, Research Division of Materials and Resources, Germany

b Technical University of Darmstadt, Research Division of Materials Flow Management and Resource Economy, Germany

c Fraunhofer Research Institution for Materials Recycling and Resource Strategies IWKS, Germany

Direct correspondence to Marc Widenmeyer and Rishabh Kundu.