Each year we empty staggering quantities of coal—more than a billion tonnes, which works out at comfortably more than the combined weight of every human being on the planet—into the thousand or so blast furnaces operating around the world. The iron that comes out the other end may not have much carbon embedded in it, but its production entails the creation of enormous quantities of CO2—around 7–8 per cent of the global total. No other source of greenhouse gases is quite so concentrated into such a small number of sites.
