Japanese homemaker Maki Watanabe carefully pours into a plastic bottle the oil she used to cook her deep-fried aubergines, doing her part in her Tokyo kitchen for a national effort to ramp up production of eco-friendly jet fuel. “It would take a tremendous amount to make an aircraft fly, so I hope we can collect more,” said Watanabe, whose penchant for cooking allows her to donate about 40 litres (10 gallons) a year. Her contribution is pooled at a nearby supermarket that is among roughly 300...