SeaWorld Orlando rolled out two new hydrogen-powered shuttle buses Wednesday, joining an experimental program that already powers similar buses to Orlando International Airport and the Orange County Convention Center.

The new buses will be used to shuttle Busch Entertainment Corp. employees between the company's three Orlando parks -- SeaWorld, the Discovery Cove luxury resort and the soon-to-open Aquatica water park -- and the company's off-site offices.

Busch Entertainment might eventually use the buses, or more like them, to shuttle park visitors who want to take in more than one park, as Walt Disney World does with its bus system. But such an option will have to wait for the hydrogen-bus pilot project to run its course, and for SeaWorld to assess the demand among visitors who might want to visit SeaWorld and Aquatica on the same day.

 "Right now, it's primarily going to be used for just allowing that movement of our employees between the three parks," said Kelly Bernish, SeaWorld's director of environmental health and safety.

SeaWorld's 12-passenger shuttle buses are Ford E-450s, powered by internal-combustion V-10 engines modified to run on hydrogen rather than gasoline. Their emissions are almost entirely water vapor. They deliver a 99.7 percent reduction in carbon-dioxide emissions.

Bernish said SeaWorld wants to explore expanding the use of hydrogen fuel, or biodiesel fuel, vehicles throughout the company's fleet. Rivals Universal Orlando and Disney World already have converted many of their vehicles to biodiesel fuel.

Technology Ventures, The hydrogen-fuel bus program involves a partnership of Ford Motor Co., ChevronProgress Energy Corp. and the Florida Department of Environmental Protection's Florida Energy Office. The buses will refuel at a hydrogen station that the state opened last year on Boggy Creek Road, not far from Orlando International.

Ford is delivering 30 of the buses to customers across North America as part of a test fleet. The Greater Orlando Airport Authority and the Orlando Convention Central District got the first of the vehicles last spring.