Dynamic prospective life cycle assessment of transition paths for the Austrian steel industry

Background On its path to achieving climate neutrality targets, the emission-intensive crude steel industry is undergoing a fundamental transformation in terms of its technologies, energy carriers and reducing agents. Such a fundamentally changing system requires an environmental assessment from a forward-looking and time-differentiating perspective. This paper proposes a dynamic prospective life cycle assessment of the transition paths of the Austrian steel industry, including a detailed evaluation of the relevant energy supply options. Methods The assessment is based on Prosperdyn, a novel dynamic inventory calculator developed by the authors as an extension to the Brightway package. It combines dynamic foreground scenarios with prospective background data, taking into account the global transformation. Compared with other available tools in this field, pathway variations can be calculated in significantly less time, enabling them to be modified according to a normative emission target. The climate impacts of steel production are assessed alongside the emissions from the construction of the electricity and hydrogen infrastructure in a dynamic impact assessment. This includes additional radiative forcing as a complementary metric to the global warming potential. Results Prosperdyn was employed to model the transition of crude steel production from blast furnaces to direct iron reduction using hydrogen by 2050. By iteratively modifying the transition path, the global warming potential will decline linearly from now until 2050, in line with the normative net-zero emission target. The final technology path meets the greenhouse gas budget and limits long-term radiative forcing. Conclusions The results demonstrate that achieving the targeted emission reductions requires a combination of ambitious measures. These include switching early to alternative reducing agents and increasing the share of secondary steel. In contrast, the source of renewable hydrogen has a minor impact on greenhouse gas emissions, but considerably affects the expected primary energy demand.