The first gas station in a major city to sell vegetable fuel for diesel cars and trucks opened yesterday in San Francisco. A similar station also opened in Sparks, Nev. The biodiesel fuel is made from recycled vegetable oil from restaurants or from soybean oil. The fuel doesn’t cut back on nitrogen oxide emissions, but it does avoid the carbon monoxide problems and the cloud of particulates that come from burning diesel. Vehicles using biodiesel experience a small drop in fuel economy, and give off the scent of french fries. Teri Shore, from the enviro group Bluewater Network, said biodiesel could help with the U.S.’s energy problems: “Instead of mining in the Arctic National Wildlife Refuge, we can mine the nation’s supplies of restaurant grease.”