Future environmental impacts of metals: A systematic review of impact trends, modelling approaches, and challenges
Carina Harpprecht, Brenda Miranda Xicotencatl, Sander van Nielen, Marc van der Meide, Chen Li, Zhijie Li, Arnold Tukker, Bernhard Steubing
Abstract
With the energy transition, the future demand for many metals is expected to sharply increase. We systematically reviewed studies which assessed future environmental impacts of metal supply chains. We evaluated their results regarding future impact trends, and their methods, i.e., modelling approaches, scenario variables, and data sources. Our review yielded 40 publications covering 15 metals: copper, iron, aluminium, nickel, zinc, lead, cobalt, lithium, gold, manganese, neodymium, dysprosium, praseodymium, terbium, and titanium. Metals crucial for the energy transition, e.g., lithium or neodymium, are rarely addressed, unlike major metals. Results for future environmental impacts of metals strongly depend on scenario narratives and assumptions. We found that specific impacts (per kg) may decrease driven by, e.g., greener electricity, higher recycling shares, or novel technologies. Nevertheless, this is probably insufficient to compensate for surging demand. Thus, future demand-related impacts are still likely to increase. We identified 15 scenario variables. The most common variables are background electricity mix, ore grade, recycling shares, demand, and energy efficiency. It is crucial to better understand future impacts of more metals, considering also rising demand and impacts beyond GHG emissions. We recommend improving research practices towards open and collaborative research, to enable more harmonised, reusable and accurate scenario assessments.