Energy companies are planning to revive a polluting technology developed by the Nazis to replace dwindling supplies of oil with synthetic fuels derived from coal. Senior industry figures told a high-level conference in Paris this week that coal-to-liquids (CTL) technology could fuel cars and aircraft for decades to come. Green campaigners reacted with alarm because the process produces twice as much greenhouse gas as using oil. Supporters say much of the carbon pollution could be captured and stored underground, and that the synthetic fuel burns cleaner than conventional diesel.