Christina Wulf

Lessons Learned from a Life Cycle Sustainability Assessment of Rare Earth Permanent Magnets

Summary In order to address methodological challenges during life cycle sustainability assessment (LCSA), this article combines the results of a life cycle assessment (LCA), a life cycle costing, and a social LCA using the example of a complex product: a rare earth permanent magnet for use in wind turbines. The article presents different approaches for combining the results of separate assessments with its attendant methodological challenges. Different normalization, aggregation methods, and weighing factors are applied and their impacts on the results are compared. The underlying case study makes an evaluation of these different methodologies more concrete. Results show that the normalization method applied has a greater influence on the overall results than the aggregation method or weighting factors. Additionally, this study shows that indifference thresholds should be applied to avoid overestimation of small impacts. Indifference thresholds ensure that impact categories with nearly the same results for all analyzed options are treated as identical results. The study also indicates the importance of the question of how much compensation between impacts is desirable. Despite the impact of these factors, the chosen case study of an LCSA for permanent magnets with different supply routes for rare earths shows that the ranking of Chinese production is the most problematic irrespective of the approaches applied.

Power-to-Gas—Concepts, Demonstration, and Prospects

Abstract Power-to-Gas is a concept to store electricity long term in generation systems dominated by renewable electricity sources, to produce fuels for transportation, household, and industry, or to offer flexibility in demand. Most process steps within a Power-to-Gas system are not new and are mostly mature and already part of the conventional energy system, for example, pipeline transportation of gaseous energy carriers. Electrolysis, however, needs to be fit to the requirements of Power-to-Gas because renewable or excess electricity are only temporarily available. The different electrolysis technologies are discussed in this context. Another special process is the methanation. Two different concepts, catalytic and biological methanation, are available. Both technologies are discussed regarding process design and development status. Furthermore, in Europe, 106 Power-to-Gas projects are known. They are analyzed in terms of their concepts, processes used, and other important parameters. Most of the projects are located in Germany. Other countries, however, have shown increasing interest in the last years. Results of an analysis of energy supply scenarios for different countries point out that the Power-to-Gas potential is locally very different and depends highly on the future development of the different national energy systems.