Abstract
Amid present concerns over a potential scarcity of critical elements and raw materials that are essential for modern technology, including those for low-carbon energy production, a survey of the present situation, and how it may unfold both in the immediate and the longer term, appears warranted. For elements such as indium, current recycling rates are woefully low, and although a far more effective recycling programme is necessary for most materials, it is likely that a full-scale inauguration of a global renewable energy system will require substitution of many scarcer elements by more Earth-abundant material alternatives. Currently, however, it is fossil fuels that are needed to process them, and many putative Earth-abundant material technologies are insufficiently close to the level of commercial viability required to begin to supplant their fossil fuel equivalents "necessarily rapidly and at scale". As part of a significant expansion of renewable energy production, it will be necessary to recycle elements from wind turbines and solar panels (especially thin-film cells). The interconnected nature of particular materials, for example, cadmium, gallium, germanium, indium and tellurium, all mainly being recovered from the production of zinc, aluminium and copper, and helium from natural gas, means that the availability of such 'hitchhiker' elements is a function of the reserve size and production rate of the primary (or 'attractor') material. Even for those elements that are relatively abundant on Earth, limitations in their production rates/supply may well be experienced on a timescale of decades, and so a more efficient (reduced) use of them, coupled with effective collection and recycling strategies, should be embarked upon urgently.