A puzzling matter about materials, particularly structural materials, is that they exhibit both a rather extraordinary extension in time, bridging over many historical and prehistorical ages, and a dynamic dimension, changing as they are in time to the point that materials may not be easily recognized as similar today as thousands of years ago. To understand this dichotomy, it is necessary to reach beyond materials science and STEM disciplines and to collect concepts and methods from SSH. Materials and energy are at the core of the physical world in which society functions: they provide the structure of the artifacts that we need, along with the ability to make and use them. They do not exist in an absolute, Aristotelian world, but are invented along historical time, by people to meet their needs, hic et nunc. Materials are social constructs, as is the “theory” (technology, science in modern language) that gives us the keys for making them. As society changes historically, people’s needs evolve and “new” materials are created on the shoulders of older ones, in a kind of evolutionary process. This is the view of social constructivism. This evolutionary metaphor is a first explanation of the continuity between, say, iron from a Roman bloomery and steel, as a contemporary commercial product. This has been formulated as the Social Cycle of Materials (SCM) by sociologists of Knowledge and Innovation, as a process of continuous innovation in which materials are socially constructed over and over again, a process often called “progress”. The continuity from old to new materials needs to be explained by some other model, however, to be fully understood: indeed, why is iron enduring so much, when it might have been displaced by another material at each evolutionary step and it didn’t. The explanation we propose is to accept that “materials have agency”, i.e. that they themselves are the actors of their own perenniality. This refers to another model, the Actor Network Theory (ANT) of Latour et al., which analyzes how change is pulled by a combined network of actors, that include people, organizations, non-human living entities and inanimate things as well.

There is an explosion of publications and of various announcements regarding the use of hydrogen in the steel sector as a way to arrive at Net-Zero steel production − particularly in Europe. Most of them describe process technologies on the one hand and commitment to implement them quickly in the steel sector in the form of roadmaps and agendas, on the other hand. The most popular process technology is H2 Direct Reduction (H2-DR) in a shaft furnace. Available technical literature, as abundant as it may be, is still fairly incomplete in making the pathway to Net-Zero explicit and credible. This paper tries to identify important issues which are not openly discussed nor analyzed in the literature, yet. Process-wise, open questions in technical papers are: (1) what are the best-fitted iron ores for H2-DR, (2) what downstream furnace, after H2-DR, can accommodate various raw materials, (3) how and how much carbon ought to be fed into the process, (4) what is the best design for the shaft, (5) should it be designed for both natural gas and H2 operations, or simply for H2, (6) how should the progress of R&D be organized from pilot plants up to full-scale FOAK plants and then to a broad dissemination of the technology, (7) what kind of refractories should be implemented in the various new reactors being imagined, etc. Cost issues are also widely open, as a function of green hydrogen, green electricity and carbon prices. How is hydrogen fed to the steel mill and what exactly is the connection to renewable electricity? Is the infrastructure that this calls for planned in sufficiently details? What is still missing is a full value chain picture and planning from mining to steel mills, including electricity and hydrogen grids. Two years after our last review paper on hydrogen, the overall picture has changed significantly. Countries beyond Europe, including China, have come up with roadmaps and plans to become net-zero by 2050, plus or minus 10 years. However, they do not rely as much on H2 alone, as Europe seems to be doing. What is most likely is that several process routes will develop in parallel, including, beyond H2-DR, Blast Furnace ironmaking and NG Direct Reduction with CCS, electrolysis of iron ore and scrap-based production in EAFs fed with green electricity, which would single-handedly support the largest part of production by the end of the century; as more and more scrap is to become available and be actually used. There is also a question for historians. The influence of Climate Change on Steel has been discussed continuously for more than 30 years. Why has the commitment to practical answers only solidified recently?

LCA (Life Cycle Assessment) is an established method to measure the economic, social and environmental impact of a good or a service, with particular attention to its value chain or its life cycle. However, it is heavily biased in favor of environmental issues, actually environmental burdens or stressors: the economic dimension is only tackled in LCC (Life Cycle Costing) and the social in a restricted approach called SLCA (Social Life Cycle Assessment). The idea of developing a more ambitious and wider encompassing method has been elusive, except when MFA (Material Flow Analysis) was proposed as an alternative and a competing discipline, but, eventually, the two methods proposed separate but complementary views of the world. In order to reach beyond LCA and its present weaknesses, it would be necessary to base the new approach on concepts embedded in SSH (Social Sciences and Humanities) rather than in STEM (Science Technology Engineering Mathematics) disciplines. This article describes the process under way to move in that direction. In a first step, a panorama will be drawn of the strengths and weaknesses of LCA and of LCT (Life Cycle Thinking). The analysis will focus on LCA weaknesses. On the way to extending LCA into SSH territory, an approach developed by Knowledge and Innovation, Italy, and called SCM (Social Cycle of Materials) looks at materials from a historical perspective. It shows how various resolutions (closures) are proposed to answer issues raised at different times, as a result of society’s demand. The method proposes a distinctly new way of looking at materials cycles. The connection between this new approach and the traditional LCA cycle remains, however, to be done. In this paper, we propose to use ANT (Actor Network Theory), a concept developed by Bruno Latour, Michel Callon and Madeleine Akrich, to propose reconstructing the concept of LCA. The approach ambitions to list the various “stakeholders” related to materials in their value chain, like what is done in LCA, but also across long time, like what is done in SCM, and to include all actors in the sense of ANT, which means inanimate objects as well as elements of the geosphere and of the biosphere. It is expected to gain some insight into moving away from the indicator-based style of LCA. Clearly, we are still exploring and, most probably, we may end up complementing traditional LCA, most certainly not replacing it.

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