Reuters: Large increases in biofuels production in the United States and Europe are the main reason behind the steep rise in global food prices, a top World Bank economist said in research published on Monday. World Bank economist Don Mitchell concluded that biofuels and related low grain inventories, speculative activity, and food export bans pushed prices up by 70 percent to 75 percent. The remaining price rise reflected a weaker US dollar, higher energy costs and related rises in …