The metals production industry consumes a large amount of energy and resources while at the same time producing a large amount of waste. Metals and their alloys, however, are important materials essential to our society. The metal production industry has to change its attitude from a `throw-away' type mass-production to a sustainable mass-production. Recycling of `man-made' resources is the key technology to achieve this goal. In this context, recycling of `man-made' resources means not only recycling of metals in the traditional sense but also must include minimization of waste and energy consumption. In reality however, recycling, waste minimization and energy minimization are often at odds with each other. Therefore, metallurgists and materials scientists should not seek an unattainable zero-emission goal but rather develop more realistic metal production technologies achievable with our present technological and economic capabilities. The mass flow of non-ferrous metals such as Cu and Zn in Japan has been investigated and is reviewed together with various recycling processes developed within the framework of the SSM project. The SSM project is supported by Japanese government.