EDINBURGH, Scotland -- There's a theory floating around about the the carbon emissions produced by manufacturing, erecting and monitoring wind turbines actually exceed the greenhouse gases generated by fossil fuel plants. "That's garbage. I know how [the doubters] get their figures and they are absolutely wrong," said Ian Bryden, professor of renewable energy at the Institute of Energy Systems at the University of Edinburgh, in an interview. Bryden was giving us a tour of his labs. He also serves as the director of the European Marine Energy Centre. Bryden has been researching wave power for years. Some of the early experiments took place at Edinburgh. It takes about 20 months to recover all of the carbon emissions in a wind turbine, Bryden said. Wind turbines operate for two or more decades so the emissions balance is quite positive. Wave and tidal devices may be able to recover their carbon emissions in 18 months or so, he added. Right now, though, it's hard to say because the industry is in its infancy.