"Sustainable urban life is technologically achievable, and most important, highly desirable. For example, food waste can easily be converted back into energy employing clean state-of-the-art incineration technologies, and wastewater can be converted back into drinking water. For the first time in history, an entire city can choose to become the functional urban equivalent of a natural ecosystem. We could even generate energy from incinerating human feces if we so desired. We have the ability to create a "cradle to cradle" waste-free economy. All that is needed is the political will to do so. Once we begin the process, cities will be able to live within their means without further damaging the environment."