The concept of Clean Technologies can be roughly defined when one sticks to simple criteria such as that of production or the treatment of waste, but it becomes highly complicated once extended to other factors such as energy, the environment, ores, heritage, the social aspect etc. If one keeps to those fields where rroducers can act in an independent manner real examples show that clean processes do not have special reasons for being more economic than others. Producers adopt processes that prove to be both more economic and cleaner than the processes currently used quite naturally when they are not troubled by problems of depreciation, financing, raw materials, technology, etc. On the other hand, industry puts officials on their guard against a policy that would tend to lead one to believe that clean technologies are always the most economic and that, consequently, would systematically force industrialists to use these technologies without taking account of economic