In a sprawling greenhouse with shiny silver ducts running through, stacks of cardboard boxes feature prints of a flower alongside the distinctive red Toyota logo. In an experiment aimed at putting to use some of the carbon dioxide blamed for global warming, the giant auto group is using Asia's largest greenhouse for potted flowers, stretching across five acres. "Nowadays you automatically think of C02 as a villain. But it's what plants need to grow," said Teruo Takatomi, president of unit Toyota Floritech Co. Ltd. The system generates power by burning natural gas, with electricity used for lighting over plants, "waste" heat for warming water, and emitted carbon dioxide falling on plants to promote their photosynthesis. "You have gas emissions when you generate electricity. After removing nitrogen oxide from the gas, C02 is returned here for plants to inhale," farm chief Takuya Sato said, pointing to the overhead ducts. The new system introduced in March is expected to help the company slash C02 emissions by a combined 460 tonnes a year, he said. The farm is the first large commercial facility in Japan to introduce a form of "trigeneration" system