Safeway grocery trucks no longer just deliver vegetables. In a sense, they now run on vegetables, too. Safeway, the nation's third-largest grocery chain, said Friday that its entire nationwide trucking fleet now uses biodiesel, a renewable fuel that can be made from plant oils, used cooking grease or animal fat. In Safeway's case, the biodiesel comes from soy oil or canola oil. It is blended with regular petroleum diesel before being pumped into the company's more than 1,000 trucks. The move is part of Safeway's broader effort to green its operations. The Pleasanton company buys much of its electricity from wind farms, has switched to energy-efficient refrigeration and lighting, and is installing solar panels on 24 of its California stores. Biodiesel generally produces less air pollution than diesel made from petroleum. And it helps rein in greenhouse gas emissions because the plants used to make it absorb carbon dioxide from the atmosphere. Safeway won't reveal how much fuel it's buying or the price it's paying. Biodiesel typically costs more than regular diesel. The price increased last year as some farmers switched from growing soybeans to growing corn, hoping to tap into the growing market for another alternative fuel - corn-based ethanol. Safeway estimates that using the biodiesel blend will cut the company's carbon dioxide emissions by 75 million pounds each year, the equivalent of taking 7,500 cars off the road.