From John Kitchen, Kettering, Northamptonshire, UK
Almost all of the problems with the mining of minerals vital to renewable technologies like electric cars can be solved by newer technologies: zero-rare-earth magnets, zero-rare-earth electric motors, zero-lithium supercapacitors(23 August, p 36).
The only remaining requirement will be copper. It is even possible that a form of carbon could replace copper in many applications.
