Contra Costa Times: A hungry student at the University of San Francisco last week couldn’t find a few college staples at the campus eatery — a juicy hamburger and a cheesy slice of pizza. It was “Low Carbon Diet Day” on Tuesday, and beef and cheese were off the menu. With 18 percent of the world’s greenhouse gases emitted by livestock raised for meat and dairy products — more than cars, trucks, ships and planes combined, according to a United Nations report — more food purveyors are launching …