Environmental champion Arnold Schwarzenegger is defending his decision to drive around in a gas-guzzling Hummer, claiming that new technology allows him to use "biofuel" in his tank. The California Governor has come under fire from critics for campaigning for a cleaner environment, while driving around in a carbon dioxide-emitting sports utility vehicle. But the Terminator star, who was the first person to own one of the military cars in 1992 after persuading manufacturers to make them for non-army purposes, insists Hummer bosses are at the forefront of fuel-efficient, green technology. He tells Men's Journal magazine, "There's already the technology to build a hydrogen-fuelled Hummer. "We got in touch with General Motors, and they did it. The car is travelling around the world right now. I can make my Hummer run on biofuel; it's just a little adjustment to the engine." The announcement comes just a month after former US Vice President-turned-environmental campaigner Al Gore insisted Schwarzenegger was giving up his Hummer fleet.