Economist: A RECENT American television advertisement features a series of trustworthy-looking individuals affirming their faith in the potential of “clean coal’. One by one, a sensible old lady in a hat, a lab-coated scientist standing by a microscope, a fresh-faced young schoolteacher, a weather-beaten farmer and a can-do machinist face the camera square-on and declare, “I believe.’ The idea that clean coal, or to be more specific, a technology known as carbon capture and storage (CCS), will …