Economist: MANY people consider the wider use of biofuels a promising way of reducing the amount of surplus carbon dioxide (CO2) being pumped into the air by the world’s mechanised transport. The theory is that plants such as sugar cane, maize (corn, to Americans), oilseed rape and wheat take up CO2 during their growth, so burning fuels made from them should have no net effect on the amount of that gas in the atmosphere. Biofuels, therefore, should not contribute to global warming. Theory, …