What are the Goals of Sustainable Metallurgy?

Sustainable metallurgy is a holistic and systemic approach of producing metals in a manner that balances engineering, economic, social, and environmental considerations. This approach can be grouped along a few main pillars, namely, environmental sustainability, economic viability, social fairness, resource efficiency, physical and chemical foundations of the required processes, and disruptive innovation strategies.

Environmental sustainability refers to reducing the environmental impact of the entire metal production chain, with the most essential and urgent goals of reducing greenhouse gas emissions, minimizing water and energy use, and reducing waste production.
Economic viability includes producing metals in a way that is economically rewarding and profitable, while also ensuring that the underlying and downstream industries are themselves resilient and sustainable in the long term.
Social fairness refers to the sustainability of the consequences that the transition toward a more circular economy has on society, referring explicitly to the global society.

This means that sustainable metallurgy includes the task of ensuring that the industry is socially responsible, by providing safe and healthy working conditions for employees, respecting the rights of local communities, and promoting fair labor practices. A socially responsible approach to sustainable metallurgy must ensure that sustainability gains in wealthy regions are not created by suffering in less wealthy regions of the globe. This means that it cannot work by exporting all the health risks and poor labor conditions associated with mining and production of the additional metals needed for a more sustainable technology infrastructure to low-wage regions. This would create a global imbalance where sustainability gains in rich parts of the world are bought at the costs of the suffering of poor parts of the world.
Resource efficiency means that the use of natural resources, such as water, energy, and raw materials, is minimized in the production and use of metals.
The last two pillars of sustainable metallurgy, namely, the scientific foundations of the processes involved and the many disruptive innovations needed to revolutionize this sector, are at the core of this paper. They refer to all basic and applied questions that help to render the entire metallurgical sector more sustainable, through recycling and closed-loop systems, less energy- and greenhouse-gas-intense primary production, waste minimization, re-mining, as well as the invention and maturation of new technologies, processes, and materials. All these items must be scalable to the huge dimensions and quantities in this field, characterized by the production of about 2 billion tonnes of metals every year. As a guideline through this paper, the later points can be grouped along a few main goals and research directions, where the focus is placed particularly on topics with high leverage on reducing CO2 emissions and energy consumption:

1. Sustainable primary production of metals and alloys. This includes sustainable synthesis from primary (minerals) and ternary resources (dumped industry waste that can be re-mined) as well as more efficient and energy-saving downstream production. In essence this encompasses all efforts to extract and process chemically bound metals from raw and waste materials with less greenhouse gas effects and at lower energy consumption. The huge amounts of waste and by-products from metal production must also be considered in this category.

2. Sustainable secondary production of metals and alloys by use of scrap. This includes better collection and sorting of scrap and its use for making recycled and even upcycled metallic alloys. It also includes research on improving recycling of intensely mixed scrap where element recovery is very challenging owing to their close integration in components. A related task is to change alloy design in a way to make materials compositionally more robust and thus better suited for recycling. This means that we must rethink alloys in a recycling-oriented way that they can better serve (a) as scrap-donator for a larger variety of new materials and (b) as scrap-acceptor from a larger variety of old materials. This means that alloys must become compositionally more streamlined and lean and that the chemical variety of metallic alloys should be reduced. This turns the entire field from chemistry-dominated alloy design to microstructure-dominated alloy design. Also, in general, alloys must become more impurity-tolerant.

3. Substitution of metallic alloys, i.e. replacing less sustainable metallic materials by more sustainable ones.

4. Increased longevity of metallic materials, to avoid the products made of them being scrapped in the first place.

Of course there are many more aspects to be considered in that context in each of these categories. Examples are discussions around the general reduction in the consumption of metals for capita and more profound changes in how we live and consume goods. However, these more societal facets are outside of the scope of this paper, which aims to take a scientific view at metallurgical measures for the fast and efficient reduction of greenhouse gas emissions in this sector and which are realistic and compatible with the expected global consumer behavior. Also, it has been shown that the growing market demand for metals scales with the increase in the gross domestic product and this is particularly driven by the growth of economies in highly populated and less wealthy regions of the globe who strive to escape from poverty. It seems hence not very realistic and not fair to expect that the populations in these regions abandon their right for economic prosperity. Furthermore, the hazardous influence of greenhouse gas emissions, energy demand, and waste and by-products from metal production on the planet’s future and its relationship to the global economy and societal boundary conditions have been addressed in detail in the literature. In contrast, the exploration and reflection of the scientific foundations of how to reduce all these effects by disruptive innovations in the metal sector have received much less attention.
Many of the currently discussed engineering and technological mitigation strategies to change this system appear often as linear extrapolations from well-established synthesis and processing concepts, and some of these concepts have a moderate effect on the improvement of the sustainability of metals, particularly on CO2 emissions. They are in part rather motivated by a gradual transition approach toward more sustainable technologies, where existing technologies are integrated rather than replaced. The reason is that synthesis and processing investments in the metallurgical sector are usually huge, sometimes of billion Euro dimension. This means that wrong investment decisions can substantially harm a company or even an entire industry sector. This is also one further motivation item for conducting more basic metallurgical research in sustainable metallurgy, as better understanding is the best guarantee for making pertinent and robust investment decisions with a long-term effect paired with economic viability. This means that developing more disruptive and innovative approaches in this field, at minimized investment risk, will profit from deeper understanding of the underlying governing scientific principles, allowing identification of key bottlenecks and fundamentally new approaches with high efficiency for a sustainable metallurgical system.

Direct and indirect sustainability of metals

Metal and alloys are usually “invisible” and “hide” inside complex products and technologies into which they are often very closely integrated (e.g., metals in mobile phones, vehicles, machines, computers, buildings, computers, power plants, or household appliances).

This makes it even more difficult, impossible, or even counterproductive from a sustainability standpoint to dismantle, retrieve, collect, separate, reuse, sort and recycle all of them. The reason for this is that the collection, sorting and recycling of metals, depending on their degree of dispersion in waste and scrap, can in some cases even generate more greenhouse gases and can have a higher energy consumption than if the same materials are produced via primary synthesis, i.e. from minerals. Such competing sustainability scenarios can be evaluated through life cycle assessments, (57,99−104) which, however, are not the subject of this article. In other words, measures that may appear sustainable do not necessarily have to really be sustainable.
The fact that the production numbers in the metal sector and the environmental harm caused by it have such a huge magnitude qualify metallurgical sustainability research as an important and urgent research topic, with significant leverage on the future of an entire industry. Solving fundamental questions in this field requires inclusion of methods from metallurgy, mechanical engineering, physics, manufacturing and chemistry. The scientific challenges but also the research opportunities in this field are enormous. This makes the topic appealing to a new generation of researchers with a highly interdisciplinary approach to materials science. The reward is to conduct research that has high impact and significance for a sustainable society and industry.

The sustainability of metallic materials can be grouped into two main categories, direct and indirect sustainability.

The former refers to all measures that help reduce the environmental burden associated with the synthesis and manufacturing of metals and alloys, i.e. primarily the reduction of their carbon, energy, and waste footprint associated with production. The latter refers to all sustainability effects that metals enable through their properties, when used in products or processes. This means that direct sustainability addresses the sustainability of metal production while indirect sustainability addresses sustainability gains through the use of metallic materials