Forty years ago when rubber tire gantry cranes were first used at the Port of Long Beach, they were the latest thing in technology to move cargo containers around the port. But the 80-foot-tall green cranes with their 1,000-horsepower diesel engines guzzled 10 gallons of fuel an hour and spewed dirty emissions into the air. The port, working with Southern California Edison, is hoping to help solve that problem with a demonstration project to electrify nine of the gantries at one of its terminals.