In February, on a chilly, clear Sunday morning, Richard Branson, president of Virgin Atlantic, along with co-sponsors Boeing and GE Aviation, lured more than 200 journalists to a hangar at Heathrow to witness what they said was airline history. Everyone's eyes were fixed on a 747 as it took off on the world's first biofuel demonstration flight. Never mind that only one of the plane's engines used biofuel, and that was about 25% mixed with standard kerosene jet fuel. It was still significant, given that air travel is the fastest-growing source of global greenhouse gases, and the race to find an alternative to kerosene is now crucial. The biofuel used