Environmental and economic evaluation of materials in the design process : Eco-design for direct recycling of NdFeB magnets

Abstract

Climate change, environmental degradation, and overconsumption of natural resources constitute significant challenges that humanity must confront. To mitigate climate change, integrating environmental and economic evaluations into the design stage offers a promising perspective, aiding decision-making toward more sustainable product development. The green transition towards a fossil-free economy creates an increasing demand for specific material groups such as rare earth elements. Recycling, a central strategy within the circular economy, is being considered to address this growing demand.

This thesis has two primary objectives. Firstly, it investigated the existing state of eco-design tools that quantitatively evaluate the environmental and economic aspects of designed products. Special attention was given to life cycle thinking-based methods, such as life cycle assessment and life cycle costing. These methods, while valuable, can be resource-consuming, therefore, different simplification logics can be used to reduce the complexity of the assessment and ease accomplishing the calculations.

The second objective was to identify the key parameters influencing the environmental and economic impacts within the direct recycling process of NdFeB permanent magnets. Four distinct direct recycling route options were assessed, where the magnet was recycled as an alloy. A simplified life cycle assessment and operational cost assessment were employed for environmental and economic analyses, which highlighted the hot spot processes and parameters.

Results from the hot spot analysis underscored the significance of chemical and material usage in processes, particularly chemicals like hydrogen and nickel sulfate, as well as primary neodymium and energy consumption. By optimizing the processes, considering alternative coating materials, and employing fossil-free energy, the environmental impacts of magnet recycling could be reduced. Based on the comparison analysis between routes, it was stated that mixing primary neodymium with a recycled magnet to achieve better magnetic properties has smaller environmental impacts compared to longer processing routes such as hydrogen-disproportionation-desorption-recombination. However, the economic assessment stated that the usage of primary materials produces higher costs compared to other routes. The cheapest option according to cost assessment was to produce bonded magnets in route 4. Although, in environmental impact comparison the bonded magnet route produced similar environmental impacts with some of the sintered magnet routes.

Direct recycling offers one solution to the future’s increasing demand for neodymium. Challenges related to disassembling and controlling the recycling process parameters still need future research to create feasible supply chain routes. This thesis works as a baseline for future material eco-design development and provides insights into the most impactful environmental and economic parameters within direct recycled NdFeB magnets.