Ramen is one of the most popular soups in Japan and around the world. But how do we get rid of any leftovers? Japanese scientists and engineers have an answer. Last year, a small tourist train called the Amaterasu Railway began running on biodiesel that’s made in part from ramen broth from local restaurants. To make the biodiesel, a local trucking company extracts and refines the pork fat from the stock and then mixes it with old cooking oils used to fry foods. The biodiesel costs about the same as traditional fossil fuels, and as a bonus, it smells a lot nicer than typical diesel fumes. (Some passengers have reportedly asked conductors about the aroma of fried rice in the air.) Amaterasu’s open-air cars take visitors on a 30-minute scenic tour of the town of Takachiho, where they can see mountains, rice fields, and Japan’s tallest train bridge, which stands 344 feet tall. So far, many have been impressed by the Amaterasu Railway’s new eco-friendly approach. As visitor Naoki Akimoto told Japanese newspaper The Mainichi, “It’s amazing that a sightseeing train can run on ramen soup.”