The U.S. Postal Service has decided to switch to a greener fuel for some of its fleet, the San Francisco Chronicle reported. Biodiesel is a fuel made from organic matter, like soybeans or waste cooking oil collected from restaurants like McDonald’s, and emits lower levels of hydrocarbon, carbon monoxide, and particulates. Biodiesel and ethanol, a fuel derived from corn, are two forms of environmentally friendly alternatives for the trucking industry, as future legislation will require decreased emissions of harmful greenhouse gases. The service will use the biodiesel in 253 heavy-duty vehicles at the central mail depot in San Francisco, which serves that city as well as Oakland and other local areas.