Guardian: Oil giant Shell misled the public when it claimed in an advertisement that its giant $10bn oil sands project in northern Canada was a "sustainable energy source", according to the Advertising standards authority. The tar sands cover over 140,000 square kilometres of Alberta and contain nearly 173bn barrels of oil in the form of bitumen. This is strip-mined from vast open pits and the bitumen is then heated, using far larger amounts of energy than in normal oil operations, therefore …