From Scott Mendham, Sydney, Australia
The fly ash left after burning coal only contains a small proportion of lithium. If the ash is used for the extraction of this metal, what will happen to the other 99.8 per cent of this waste, which includes arsenic, lead, mercury, radioactive elements and added chemicals used in the extraction? Fly ash is a major environmental issue, but mining it for 0.2 per cent of its content could make the problem worse, especially when recycling used lithium would be a superior alternative to boost supplies (18 November, p 22).
