120717-N-ZG290-107 PACIFIC OCEAN (July 17, 2012) Aviation Boatswain's Mate (Fuels) 3rd Class Joshua Palomares checks the specific gravity of biofuel with a thermo hydrometer in the quality surveillance fuel shop aboard the aircraft carrier USS Nimitz (CVN 68) during a replenishment at sea. Nimitz took on 200,000 gallons of a 50-50 blend of advanced biofuels and traditional petroleum based fuel during the U.S. Navy's Great Green Fleet demonstration portion of the Rim of the Pacific (RIMPAC) 2012 exercise. (U.S. Navy photo by Mass Communication Specialist 3rd Class Devin Wray/Released)