Sustainable Recycling of Critical Materials

Abstract

The world’s supply of critical materials such as phosphorus (P), niobium (Nb), lithium (Li) and other strategically important elements is under increasing pressure due to the rapidly growing global demand in the recent years and limited possibilities of substitution. These materials are used in producing a broad range of products in everyday life and forming an integral part of many advanced and clean energy technologies. Hence, such materials are significant for many industrial sectors and essential to societal wellbeing. Therefore, the steady supply of critical materials starts to be one of the key economic and environmental questions. Moreover, the analysis of flows of those materials coming from mining and recycling starts to evoke the growing interest.

A systematic understanding of how such materials flow through the industrial and residential sectors is required. Such awareness of materials’ inclusion in various products and their current stocks in the anthroposphere improve the potential of recycling and reuse of those materials as well as minimize overall waste.

This dissertation presents dynamic models for critical materials such as P, Nb, and Li by using system dynamicsmethodology. It considers all stages of supply chain by addressing material and energy flows as well as greenhouse gas emissions. The main finding assists in optimizing for environmentally sustainable operations in designing and modelling of the critical materials supply chain.

The findings indicate a clear need to analyse the recycling processes carefully. The obtained results show that recycling of used products containing critical materials, in some cases, aims to prevent the shortage of those materials and contributes to developing a robust circular economy. However, the environmental sustainability of recycling procedures for all materials could not be taken for granted, because it could differ based on the type of the waste stream. For some critical materials, recycling can cause more environmental damage than mining. Therefore, we should not treat critical materials as a homogeneous group. Recycling carried out using the existing technologies is a partial solution for some materials. In addition, there are physical limitations to the increasing of the recycling rate for some materials. The main limiting conditions of recycling can be economic, environmental, and physical by nature. The lattermost means that even if recycling is both more profitable and “greener” than mining, it is still impossible to completely replace primary production with the secondary one.